A comprehensive comparison from parallel TV ... - cb-cda.gc.ca · existing PMT panel, where no re-processing is required and the next day’s estimates are also the final estimates

ESOMAR / ARF WAM Conference – TelevisionGeneva (Switzerland), June 2004

© Copyright by ESOMAR® / ARF

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The authors report findings from an extensive analysis comparing two TVmeter panels in Québec, Canada; the TNS Picture Matching technology(PMT) and Arbitron’s Portable People meter (PPM). Paramount in thiscomparison is the passive nature of reported viewing in the PPM panelversus the button-pushing task required of the PMT panel. Running inparallel for almost one year, the panels reveal important information oncompliance in both the “carrying” task and the button pushing task,individual viewing behaviour, the efficacy of the PPM technology in acomplex TV measurement environment, and the reasons for differences inthe audience measurements. The authors provide an assessment of degreeto which various factors impact the ratings differences between buttonpushing and passive meter systems, and argue that button-pushing non-compliance accounts for most of the difference.

PASSIVE VS. BUTTON PUSHING

A comprehensive comparison from parallel TVmeter panels in Québec

Pasquale (Pat) PellegriniKen Purdye

Pasquale (Pat) Pellegrini, Ken Purdye


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BACKGROUND

The Personal People Meter (PPM) is an audience measurement systemdeveloped by The Arbitron Company in the United States. It requirestelevision and/or radio stations to place an identifying audio code and a timestamp in their output, using a special encoder. The code is inaudible and itsinsertion and transmission are completely automatic. A sample of thepopulation is chosen and equipped with a small carry-around device similar toa pager. This device “listens for”, detects and stores the codes extracted fromthe broadcasters’ output together with a time stamp. It is provided with amotion detector to verify that the respondent is in fact carrying it around. Thedevice provides a completely passive record of sample respondents’ exposureto radio and television signals. There are no buttons to push, no diary recordsto be kept. At the end of the day, before the survey respondent retires for thenight, the carry-around device is placed in a dock connected to the household’spower line and telephone. While in the dock the carry-around device’s batteryis recharged and its data downloaded to BBM.1)

BBM Canada was an early believer in the Arbitron PPM system and has heldthe Canadian rights to its use for a number of years. This new audiencemeasurement system seems to us to offer several advantages over aconventional push-button people meter. First, it offers the promise of breakingfree from the increasingly onerous task of physically monitoring all of theelectronic equipment in panel homes. Traditional push-button meters measurethe signal viewed by monitoring the television set and associated devices suchas VCR players. New technology such as personal video recorders, recordableDVD players, HDTV receivers and internet delivery of television programsmake this an increasingly risky enterprise. The PPM, by contrast, monitorsviewing directly from the program viewed, without the necessity for anyintermediate steps.Another promise of the system is that it links the automatic detection ofbroadcast signals with the individual viewing them. It eliminates the need forpanel members to push buttons, viewed by many as the Achilles heel ofexisting people meter systems. This has been one of our major pre-occupationssince the introduction of people meters to Canada (Pellegrini and Purdye,2002; 2003). If the respondent can hear the signal, the viewing or listening isautomatically recorded without the need for special intervention. In addition,PPM offers the opportunity of measuring both television and radio on acomparable basis thus making a start in true multi-media measurement. This isan important factor for BBM, since it is responsible for measuring theaudiences to both radio and television in Canada.

Passive vs. button pushing


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Finally, and most importantly, PPM is a priori a system which can be operatedat a lower cost than the conventional people meter: it requires lessinfrastructure (a field force of engineers, multiple reference sites, etc.). Withincreasing audience fragmentation, there is growing demand for larger samplesizes to maintain statistical reliability – a demand very evident in Canadawhere we have access not only to our own television and radio signals, butalso to those of our neighbour to the south. A lower cost system offers at leastthe promise of larger sample sizes for the same investment.BBM participated in some of the earliest technical tests, including “placebo”carry-around tests and the encoding of a classical music FM radio station overan extended period in 1993. The station received no complaints or queriesfrom its many listeners about degradation of its signal during this time, whilewe verified detection of the code under different listening conditions.These tests demonstrated to us that the PPM was feasible as well as beingdesirable: the encoding worked, was inaudible and there was a good chancethat the great Canadian public could be convinced to carry the thing around.BBM started installing its first PPM panel in the spring of 2003, amongFrench-speaking respondents in the province of Québec. BBM currentlymeasures television audiences in Québec using the picture matching peoplemeter system (PMT) developed by TNS (Pellegrini and Purdye, 2002). BBMalso conducts semi-annual diary surveys, which are used to measure televisionand radio audiences for each of the ten local markets in the province.The new PPM panel is initially intended to collect information on televisionaudiences only; there is currently no measurement of radio audiences usingPPM although testing is planned. (Panel members are in fact told that theirPPM devices measure television and radio, but this is done simply toencourage co-operation and carry around of the PPM). A special industrycommittee is currently responsible for declaring the panel ready forcommercialization. At that point, BBM will begin to dismantle its peoplemeter panel, and the PPM will have its first commercial incarnation, with theresults used to trade television time.The Québec PPM panel was recruited in exactly the same two-stage process asthe push button people meter panel that it was designed to replace. The twosystems, PPM and the picture matching-people meter (PMT) have beenoperating in parallel since September 2003, offering a unique laboratory for in-depth comparisons. We turn now to a discussion of the extent to which thehopes for PPM technology, outlined above, have been transformed into reality.The paper begins with initial results and comparisons with the button pushingpanel (PMT), and devotes considerable attention to the differences in reportedaudiences.



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INITIAL RESULTS

1. EncodingEncoders are currently deployed in 99 different television stations, which intotal represent, coincidentally, about 99% of all television viewing in Québecas measured by the existing PMT panel. We have experienced none of theproblems of broadcaster co-operation in encoding that critics of such systemssometimes talk about. This may be due to the unique place of BBM Canada inCanadian broadcasting: it is an industry-owned, non-profit audiencemeasurement institute. Many of the broadcast signals watched in Québecoriginate in the United States and have been equipped with encoders, with theco-operation of Arbitron. In addition, the 99 encoders have in general operatedautomatically and flawlessly.

2. Panel response ratesAs mentioned earlier, the carry-around device is equipped with a motiondetector which provides a built in edit rule for acceptance into tabulation for agiven day. If the device shows less than a minimum amount of motion per day,the viewing record for that day is rejected. Some critics of the PPM approachto audience measurement have contended that ordinary people will not carryaround the device with them and that the task is too great compared withpushing buttons. The motion data collected from respondents’ PPMs show thatthis is not the case.Currently the motion minima are set at eight hours for respondents aged 12and over and five hours for children: respondents with less than this amount ofmotion are not accepted into tabulation. Initially this threshold was adoptedfrom earlier testing of the PPM in other contexts, but our testing of variouslevels showed eight hours to be a natural break in the carry data. Extensivetesting of different so-called qualification edit thresholds illustrated littleimpact since the vast majority of panelists are compliant.On an average day, 84% of the “in-production” sample is currently acceptedinto tabulation the next day, and this number is still trending upwards asBBM’s panel management techniques are fine tuned. Waiting an extra six daysallows more time for panel members who may have been travelling (or whomay have forgotten) to dock their devices. The in-tab rate after seven days iscurrently 5 percentage points higher at 89%. In tab rates are somewhat higheron weekdays (91%) and lower on weekends (85%). BBM’s current practice isto release “preliminary” PPM audience data to its members the day followingbroadcast and “final” numbers seven days later. This is different from theexisting PMT panel, where no re-processing is required and the next day’sestimates are also the final estimates.



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These daily response figures are lower than those for the parallel PMT panel,which regularly achieves in-tab rates of 95% or more. This is not surprising,since PMT accepts all members of “clean” households into tabulation, whereasPPM examines each member of the household separately for qualification ofthe motion criteria. An uncooperative or non-compliant member of a PMThousehold may slip under the wire; this is not possible with the PPMqualification process. The PPM process is therefore more stringent than thatused by PMT.Turnover in the PPM panel is considerably higher than that in the PMT paneland remains an issue. It is currently (February 2004) running at about 12% permonth. Most of the turnover is due to voluntary dropouts by panel members(9%), the rest (3%) being drop out forced by BBM for non-compliance. Thecorresponding figure for the PMT panel is about 1% per month (12% per year,with no forced turnover policy in effect). The dropouts tend to be youngeradults (18-34) rather than older and to be larger households with children. Thisparallels our experience with dropouts in the PMT panel, although theincidence with PPM is much higher.

3. Compliance techniquesThe need for rigorous panel management does not disappear with PPM. ThePPM devices, with their recharging units, are sent to panel homes by courierservice for self-installation. Follow-up telephone calls are made to ensure thatthis is done promptly and correctly. There is then a “break in period” for newpanel members, during which data is examined carefully and contact with thehomes maintained.BBM uses several techniques to encourage carry around compliance. Theseinclude carrying aids for the PPM (a lanyard and a wristband), reminder post-itnotes and tent cards for television sets, etc. The fact that the carry-arounddevice is equipped with a motion detector allows us to make a direct linkbetween the respondent’s task and his reward. We want the respondent to carryaround the device for the maximum amount of time every day. It is thereforepossible to link a panelist’s payment to the amount of motion recorded by hisPPM device; the reward is linked to the task without affecting the respondent’sbehaviour with respect to what is being measured, his or her exposure totelevision. Such a direct link between task and reward is not possible withpeople meter panels without biasing the measurement; it is hardly advisable toreward respondents for the amount of time their people meter button ispushed! Respondents are currently given $5 per month plus an additional$1.25 per week if 500 or more reward points are accumulated (1 point equals10 minutes of carry time). Additionally, weekly and monthly draws for $100prizes and anniversary gifts are used as incentives and rewards. A monthly



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newsletter keeps panel households informed of current panel events andannounces winners (by household identification numbers). This incentiveprogram is constantly monitored and refined using exit interviews.

4. Evidence of carry (or motion) complianceParticipants in a PPM panel are asked to do three things: undock their carry-around device when they first get up, carry it around on their person while theyare up and re-dock the device in the evening when they retire. The evidenceindicates that they perform these tasks. The median time for undocking thecarry-around device by adults is about 7.30 am, later on weekends, as wouldbe expected (8.50 am). The median time for docking the device for the lasttime at night (again for adults) is around 22:50 pm; again marginally later onthe weekends (23:15). Undocking times for teens are marginally earlier thanfor adults; docking times are marginally later.The device is out of its dock for a median 15.3 hours per day, somewhat lesson the weekends. It is also clear that when the PPM device is out of its baseunit, it is being carried around and not left lying ignored somewhere. Onaverage, the device is in motion for 14.4 hours on weekdays (about 95% of thetime it is out of its dock). On weekends the PPM is also carried around forabout 95% of the time it is out of its dock. This high ratio of motion to carrytime is evident for all subgroups in the sample. These results are comparablewith those reported by Arbitron for its Philadelphia experiment (Patchen andWebb, 2002).Another encouraging sign in the early data from the PPM panel is that theamount of recorded television exposure is uncorrelated with the amount oftime the PPM device is carried around. This would tend to refute anyhypothesis that respondents simply take the device out of its docking unitwhen they are viewing and replace it when they have finished viewing. If thiswas the case, the PPM system would not pick up any unplanned, intermittentviewing. Respondents carry the device around all the time, thereby recordingtheir exposure to both planned and unplanned viewing. This is an importantfinding should we ever extend our panel to measure exposure to radio, since itis a more mobile medium.The fact that television viewing is invariant with carry-around time isillustrated in figure 1. Hours of television viewing (per day) are measured onthe y axis and the number of hours of carrying time on the x axis. The fact thatthe plot is almost parallel to the x axis suggests that viewing and carry aroundtime are unrelated.



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Figure 1RELATIONSHIP BETWEEN VIEWING AND CARRY-AROUND TIME

OCT 27 – NOV 2, 2003

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Hours of Carry-around time

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rs o

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use

All 18+��Males 18+Females 18+

In sum, our experience suggests that people will undock, carry around and re-dock their PPM devices as required, And that they will do it in sufficientnumbers to produce satisfactory weekly response rates.

COMPARISONS WITH THE PMT PANEL

Since its inception, the PPM panel has shown higher overall television viewinglevels than the people meter panel. The difference has stabilized at around 24percent as shown in figure 2. The increase is most pronounced for children(more than double) and teenagers. For adults, the difference is 15%. It is largerfor younger adults (18-34) than for older adults (50+). This is illustrated infigure 2, which shows the average minute rating for television (PUT) over arecent six week period for different demographic groups.



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Figure 2AVERAGE MINUTE RATING

MO-SU 2:00 AM-2:00 AM, JAN 5-FEB 15, 2004, BY AGE GROUP

18.0

8.8

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The increase is more pronounced on weekends than during the week. Foradults 18+, for example, the overall difference is 15%. The difference is 26%on Saturdays, 16% on Sundays and 13% on the average weekday. This patternapplies to all age-sex groups.



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Figure 3MINUTE RATINGS THROUGHOUT THE DAY, ADULTS 18+

AVERAGE MONDAY-FRIDAY, JAN 5-FEB 15, 2004

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The difference in viewing levels between the two systems is maintainedthroughout the day but is a little more pronounced during late-night periods, alittle less for the early fringe period (16:00-18:00). This is illustrated in figure3 with information for adults 18+. The two curves show usage of televisionquarter-hour by quarter-hour for an average weekday in January-February2004. Both curves show the familiar (Canadian) pattern of gradual growththroughout the day, with a small peak at noon and a large peak in prime time.Again, the agreement between the two measurement systems is good for all thesample subgroups we have looked at. Each has its own nuance, as may beillustrated in a corresponding chart for teens (12-17), shown as figure 4.



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Figure 4MINUTE RATINGS THROUGHOUT THE DAY, TEENS 12-17

AVERAGE MONDAY-FRIDAY, JAN 5 – FEB 15, 2004

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Of interest here is the fact that the two curves are identical for the period whenthis group can be expected to be out of home at school, 08:30 to 16:00.(Experience has shown that very few teenagers will or are allowed to carrytheir PPMs to school). The differences between the two systems are confinedto early fringe and (particularly) prime time. While these differences are large,the pattern of television use is similar.This similarity of pattern of viewing by time is summarized in figure 5, whichshows the average minute PUT levels according to the PMT and the PPMpanels, for different time blocks. The overall difference is about 24%.Differences by time block are within a tight range of this mean (+13% to+24%) with the exception of the early fringe period (+10%) and the late nightperiod (+67%).



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Figure 5MINUTE RATINGS AUDIENCE BY TIME BLOCK, 2+

JAN 5 - FEB 15, 2004

18.0

12.113.2

15.0

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38.439.9

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Although PPM yields higher estimates of television use than the people meterpanel, there is little difference in the share of audience attributed to differentstations or types of station.

Table 1AUDIENCE SHARES (2+): MO-SU 02:00-26:00 JAN 5 - FEB 15 2004

Station Group PMT PPMCanadian Conventional French 58.6 57.9TVA 27.5 27.1TQS 14.5 14.6SRC 13.6 13.1Télé-Québec 3.0 3.1Canadian Specialty French 32.1 34.5Canadian Conventional English 3.3 3.1Canadian Specialty English 2.5 1.8U.S. Conventional 1.4 1.7U.S. Specialty 0.9 0.8



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This is illustrated in table 1. The four major French language networks have ashare of 58.6% in the PMT panel and 57.9% in the PPM panel. This closecorrespondence of audience shares is paralleled in most demographicsubgroups, with the notable exception of children.We have also compared program ratings for the PMT and PPM systems.Taken as a whole, the program ratings for the four French language networksshow a remarkable agreement. In one analysis over a four-week period inJanuary-February 2004, the correlation coefficient for all respondents 2+ was0.97. High coefficients (.95 - .98) were also observed for all adult samplesubgroups. The levels of agreement for teens and children, while stillsignificant in a statistical sense, were lower (coefficients of .70 and .78respectively).Of interest is the fact that the variance of program ratings is slightly less in thePPM data set than the PMT data set. For example, for adults 18+, thecoefficient of variation (standard deviation divided by the mean) for PMTratings was 1.07 and for PPM ratings was 1.03. This is repeated to a greater orlesser extent with all sample subgroups, including children and teens and isreminiscent of a similar finding when BBM first made the switch from diarysurveys to people meters: meter program ratings showed less variance thandiary program ratings. We return to a discussion of this finding later.Does the PPM data reflect PMT findings on viewer behaviour withintelevision programs? To answer this question, we examined a large number ofprograms and episodes, comparing the minute by minute program audiencesproduced by the two systems. We looked at a broad range of programs, halfhour, one hour and more than one hour, programs where PMT showed littleintra-program audience movement and a lot of intra-program movement,programs with growing audiences, stable audiences and declining audiences.One example is given in figure 6.The example is for “Auberge du chien noir”, a highly-rated téléroman that airson SRC between 20:00 and 21:00 on Mondays. As is evident, the two curvestrack each other very closely, showing the same peaks and valleys, with thePPM curve lying above the PMT curve. The correlation coefficient is 0.70.The average correlation coefficient, over all programs analysed was 0.67. Notethe tendency for the minute to minute variations to be larger with PPM thanwith PMT. The average coefficient of variation (standard deviation divided bythe mean) across all programs is 12 percent for the PMT data; for PPM it is 14percent.



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Figure 6MINUTE BY MINUTE AUDIENCE FOR L’AUBERGE DU CHIEN NOIR”

2+, NOVEMBER 2003

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We may summarize these comparisons as follows. The PPM data shows thesame patterns of viewing (by daypart, by day, choice of programs, shares ofaudience, minute by minute behaviour, etc.). However, it provides consistentlyhigher estimates of audience size than the traditional push button meter.

REASONS FOR THE DIFFERENCES

We are of course curious as to what could lie behind the differences shown inthe preceding section and the remainder of our paper deals with this subject:why does PPM provide higher estimates of television use than PMT? Ourpaper examines five possible sources: differences in the composition of thetwo panels, out of home viewing, unmeasured television sets, incidentalviewing and non-compliance in both the PPM and the PMT panels.

1. Sample characteristicsDifferences in sample characteristics may occur at three stages: the initialEstablishment Survey, the sample recruited from the Establishment Surveyand the daily in-tab sample. Both panels (PPM and PMT) use a two-stagesample selection procedure. A large Establishment Survey provides a frame



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for recruitment of the panel. The sample in each case is selected using standardRDD techniques and conducted by telephone. In each case, the surveys areconducted continuously throughout the year. The response rates for the twoEstablishment Surveys are similar.Panel replacements are selected by examining the balance of the existing panelon a range of variables (age-sex groups, geography, method of TV reception,household size, mobility, number of television sets, etc.). Replacement homesare sent a pre-recruitment package by courier. The package containsinformation on what is involved in becoming a panel member as well as asmall premium. The homes are then telephoned and recruited to the panel. Thecontent of the package and the telephone call varies between the PPM andPMT panels, since the nature of the task differs.The panel recruitment processes are similar for the two systems and theyachieve the same response rates, but different people may be attracted to takeup a PPM offer and a push button (PMT) people meter offer. However, such adifference would not be revealed by analysing the composition of the twosamples on the control variables: by definition, the two samples areapproximately the same at all times simply because they are control variables.Examination of other variables is difficult, because of the higher rate of itemnon-response in the PPM sample. Questionnaires on background variables areadministered by the field technician on installation in the PMT sample.However, the PPM is self-installed and we rely on the respondents to returnself-completed questionnaires, except for the control variables, answers towhich are collected on the telephone as part of the post installation routine.Nonetheless, taking this into account, an exhaustive comparison between thetwo panels using these non-control variables failed to detect any significantdifferences. (The variables included occupation, household income, homeownership, ownership and use of a home computer as well as a variety oflifestyle variables).The PPM sample is more tightly controlled than the PMT sample: recruitmentand balancing is done for the Montréal area and the balance of Québecseparately for PPM, but for the province as a whole for PMT. The sameapplies to weighting: for PMT, the whole province is weighted together. ForPPM the two geographical components are weighted separately, although thesame rims are used in each case. (The difference in procedure is due to arequirement to produce separate audience estimates for the Montréal area withthe PPM sample).The recruited panel is then examined every day, with results from panelhouseholds accepted into or rejected from daily tabulation. The rules foracceptance for PPM and PMT clearly differ since they are two radicallydifferent technologies. And, as we have seen, PMT daily response rates (in-tab



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divided by in-production) are consistently higher than PPM daily responserates.There may therefore be differences in the composition of the daily in-tab dueto differences in rejection rules, and these may not be corrected by theweighting process. However, we have looked for any differences in samplecomposition with respect to the weighting and control variables, withoutsuccess. For example, figure 7 provides information on the distribution of thetwo in-tab samples for an average day over the six week period Jan 5-Feb 152004, for the variable household size.

Figure 7DISTRIBUTION OF PMT AND PPM RESPONDENTS

BY HOUSEHOLD SIZE. JANUARY 2004

12.2

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Similar results could be provided for the other weighting and control variables.Our conclusion is that differences in sample composition are not contributingto the differences in observed results between the two panels, or if they are,they are not associated with the control variables.

2. Out of home viewingThere are two types of out of home viewing: viewing by panel members inother peoples’ homes and viewing in other places. PPM collects informationon viewing in other peoples’ homes directly – it is currently indistinguishable



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from a panellist viewing in his own home. PMT collects the information byproxy: it factors in viewing by guests in panel homes. For Québec, this sort ofout of home viewing in PMT is about 3.5% of total viewing among allpanelists 2+. It is more important for younger subgroups like children (9%),teens (7%) and 18-34 year old men (8%); less important for older subgroupslike the 50+ (2%).However, it is likely that PMT underestimates such visitor viewing. The entryprocedure for guest viewing is awkward. In one version, the guest has torespond to questions about his/her age and sex and language by pushingbuttons on the remote. He/she is then assigned a button number to use for a 24hour period, after which the guest registration procedure must be repeated. Tofacilitate the process, there is a special procedure for “regular guests”, who areassigned their own buttons in the same way as family members when the panelis first signed up, or later on request. Special studies have shown that 85% ormore of guest viewing is accounted for by such pre-registered “regularviewers” who have their own buttons. This must cast doubt on whether theviewing of intermittent guests is properly captured. Does it really only accountfor 15% of all guest viewing? When TNS moved to a simpler guest entry forits people meter systems, visitor viewing increased. (This system simplyinvolves indicating the number of guests in different age/sex groups who areviewing). The Québec PMT panel uses this simpler system.The second type of out of home viewing, viewing in other places, is notcaptured by PMT but is by PPM. It includes viewing in, for example,collective living establishments like college residences, public places like barsor airports, etc. There was a flurry of activity in measuring this type of viewingvia special recall surveys in the 1990’s (see, for example, Stipp and Pounds,1994 and Rosen, 1994). These studies showed that such viewing was mostcommon among young men, and for sporting events. On average, this type ofviewing represented about a quarter of all out of home viewing – i.e. about 1%- 2% of total viewing on average.Our conclusion is that in total, the contribution of this factor to the explanationof the observed differences is probably quite trivial. It accounts for maybe 2%- 3% of the overall difference of 23% between PMT and PPM. Its importanceis likely greater for the groups that show the largest overall difference betweenthe two systems (children, teens and younger adults).

3. Unmeasured TV setsIf there are non-measured TV sets in a PMT people meter home, then anyviewing to them will go unreported. Theoretically, this could cause under-reporting of television use and account for some of the difference betweenPMT and PPM viewing levels. (Obviously this is not an issue with PPM, since



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the measurement does not depend on monitoring television equipment). Asmost people meter panel operators, BBM offers a cash bonus to panelists whoreport new television equipment in their homes. Use is also made of theregular contact with panel homes to verify changes in status. The onlyevidence we have on the extent of this problem is anecdotal, that it is a veryrare event for a technician calling on a panel home to discover unmonitoredequipment.

4. Incidental ViewingMembers of the BBM PMT panel are instructed to log themselves in as“viewers” when they are in the same room as a television set that is on. Theyare to log themselves out when they leave the room; the system automaticallylogs them out when the television set is switched off. PPM respondents arecounted as “viewers” when their PPM device picks up a recognizable codeembedded in a broadcast signal. These are not equivalent definitions.It is clear that the PPM device may be exposed to TV in circumstances that thePMT panel member should not or would not consider as “viewing” andtherefore would not consider pushing a button. The PPM panelist does nothave to make a decision on whether or not to push a button, the decision ismade for him/her. This distinction may be responsible for some of thedifference in viewing levels between PPM and PMT. For want of a better term,we call it “incidental viewing”; it may be important in urban areas with largenumbers of apartments with small living spaces.At first glance, one may view the definitional difference as equivalent to“hearing” the television set without seeing it. Arbitron reported on a pilotstudy attempting to quantify this (Arbitron, 2002). The study showed that“hearing” without viewing accounted for 6% of exposure to television. Moreimportantly, it demonstrated the difficulty of asking respondents to describetheir activity during a short period of time prior to a coincidental phone call. Apositive response to a question on the telephone whether one can “hear” a TVwithout being able to see it, may mean a number of different things: awarenessthat a TV was on and part of the ambient noise, that it was a specificallydetectable noise, or that there was active listening without having a line ofsight to the television set.However, we wonder whether this is the appropriate comparison. We reallywant to compare the actual definition of “viewing” as interpreted and used byPMT respondents with the actual passive measurement of viewing picked upby the PPM device. Do we really know what definition of viewing is actuallymeasured by PMT, as opposed to the definition that is given in the panelists’instruction manuals?



18

In many open-plan residences (especially apartments and lofts), it may bedifficult to define a “room”. If the television is in the living room part of aliving-dining area and the person is in the dining area part, should they pushtheir button? If I am in the kitchen area of my home, which is not separatedfrom the living area by a door, should I push my button? Will a PMT panelistpush his/her button in these circumstances? Should he/she? We know frommany studies that much television viewing is unplanned and accidental, andthat television is often used as a “filler” activity (Clancy, 1992) or as asecondary accompaniment to other activities (Bendali and Chavenon, 1995).Even though such viewing is done “in the same room” as the television set,how much of it would result in the conscious action of button pushing?

5. Non-compliance (PMT push-button meter and PPM)In a push-button people meter world, the detection of non-compliance isperformed by automated edit rules (e.g., to detect uncovered viewing) and thevigilance of panel administrators. A respondent is always in-tab unless there issome particular reason to suspect non-compliance. Undetected non-compliersare included in the denominator for ratings calculations. If a viewer does notpush his/her button, he/she is included anyway as a non-viewer. It isimpossible to detect all non-compliers and therefore there is most probably abuilt-in downward skew to people meter ratings.The PPM world is more complex. The motion detector monitors carry-aroundcompliance; panel members’ data are rejected if a minimum amount of motionis not detected. Non-compliers are eliminated from the in-tab and thereforefrom the denominator for ratings calculations. The non-complier may be alegitimate non-viewer, but unless he/she has carried his/her PPM for therequisite amount of time (to register his/her lack of viewing), they will not bein-tab. Since it is impossible to detect such non-viewers, there may be a built-in upward skew to PPM ratings.A PPM panelist “opts in” for the day; a push button people meter panelist hasto be externally “forced out” for the day. Disentangling these two effects isextremely difficult. It is probable that they are both at work in our data. On theone hand, one can point the finger at the push button meter. We know thatthere are non-compliant button pushers, especially those who are viewing onlyintermittently with other people. (The annoying reminders on the face of themeter disappear once one viewer has logged on; there is no incentive for asecond or third viewer to follow suit). On the other hand, one can put the PPMin the hot seat: what if panelists only carry the meter when they are planning toview (or listen)? If they do not plan to view or listen, they do not undock thePPM and therefore their real “non viewing” does not get into tabulation.



19

Some evidence for this latter assertion may come from a comparison of thedemographic characteristics of those rejected from PPM tabulation for a day(because they did not undock the PPM at all, or because they did notaccumulate enough motion during the day to qualify), with those of non-viewers in the PPM system. The two groups do tend to have similarcharacteristics: they are more similar to each other than to the population ingeneral. A taste is given in table 2. This shows the distribution of PMT non-viewers and PPM rejects by age/sex group for the average day in a week inNovember 2003. Compared to the universe, PMT non-viewers and PPM non-compliers seem to be over-represented among younger adults and under-represented among older adults.

Table 2COMPARISON OF THE CHARACTERISTICS OF

PMT NON VIEWERS AND PPM REJECTS

PMT PPM

Non-Viewers Rejects Universe

A2-6 8% 7% 5%

A7-11 6% 7% 6%

A12-17 9% 10% 8%

Men

18-24 6% 6% 5%

25-34 9% 12% 7%

35-49 15% 17% 13%

50-64 6% 5% 9%

65+ 2% 1% 5%

Women

18-24 6% 5% 5%

25-34 11% 10% 7%

35-49 15% 13% 13%

50-64 4% 6% 10%

65+ 2% 1% 8%

Total 100% 100% 100%



20

Differences between PMT non-viewers and PPM rejects compared to theuniverse are less evident for other variables we have examined (reception type,household size, geographic location). By itself, this is suggestive, but nothingmore: association is not evidence of cause. Confounding the issue is the factthat neither the PPM in-tab sample nor the PMT in-tab sample reflects theuniverse for some of these categories, prior to weighting. (The 65 and over agegroup is chronically difficult to recruit for either panel).A more nuanced version of this argument links the decision to carry or not tocarry a PPM with light viewers: light viewers, it is alleged, will be less likelyto co-operate on a regular basis and therefore their light viewing will be under-represented in the in-tab sample. Fortunately, we can investigate this a littlefurther. We know, from special analyses, that those who make it into tab for allseven days of the week view more television, on average during these sevendays, than do those who fail to qualify, on the (fewer than seven) days whenthey actually qualify. This is illustrated in table 3. The first column of datashows the average hours of television viewing per day for various samplesubgroups for those accepted into tab all days and for those accepted into tabfrom 1-6 days (on the days when they were accepted into tab). The basis forthe averaging is, of course, the number of days in which a respondent wasaccepted into tabulation. The analysis is from the first four weeks of January2004.

Table 3COMPARISON OF AVERAGE HOURS OF VIEWING BETWEEN THOSE

ACCEPTED AND THOSE REJECTED BY THE PPM QUALIFICATION RULE:JANUARY 2004

In tab In tab

All days 1-6 days Include all Published

2+ 5.5 4.9 5.3 5.3

2-6 5.3 5.1 5.2 5.2

7-11 4.7 4.8 4.7 4.7

12-17 4.3 4.5 4.4 4.4

18-24 3.9 4.1 4.1 4.0

25-34 4.4 4.0 4.3 4.2

35-49 5.1 4.9 5.0 5.0

50-59 5.9 6.1 6.0 6.0

60+ 8.0 7.2 7.8 7.8



21

By itself, the difference between those accepted for all seven days and thoseaccepted for less than seven days (about 7% for the 2+ group) is not enough toexplain the overall difference between PMT and PPM viewing levels (24% forthe 2+ group). Moreover, it is not even the proper comparison: the rejects do infact make it into tab and are included in the published estimates when they do.By definition, we do not know the viewing of those rejected on the days whenthey were rejected. However, we may assume that they view the same amountof television on the days when they were accepted. If this is the case, then theestimate of television viewing would be as in column three of table 3, which isalmost identical with the actual published estimate (shown in column 4 oftable 3). What can we conclude from this? Those rejected from time to timemay well watch less television than those accepted all the time; however, thedifference is not large enough to make any difference; nor is the number ofthem (recall that average daily response rates for PPM are around 90%).It remains a seductive argument, however, and we continue to explore it. Hereis another variation. If the claim above is true, programs that attract adisproportionate number of “light viewers” should show a significantly smallerdifference in reported audience (compared to PMT) than the average. Is this infact the case? The following analysis is based on four week’s worth of data(Jan 19-Feb 15, 2004). For each program on the three main French languagenetworks, the following information was compiled:

Average minute audience in thousands (AMA (000)) according to thePMT panel (PMT2+).

AMA (000) according to the PPM panel (PPM2+). AMA (000) for quintile 1 (low viewing quintile) for the PMT panel. AMA (000) for quintiles 1 and 2 combined (two lowest viewing quintiles)

for the PMT panel. Quintile 1 as a percentage of the total audience, according to the PMT

panel (PCTQ1). Quintiles 1 and 2 as a percentage of the total audience, according to the

PMT panel (PCTQ12).

A regression analysis was run on the following two models:Model 1: PPM2+ = ß0 + ß1(PMT2+) + ß2(PCTQ1)Model 2: PPM2+ = ß0 + ß1 (PMT2+) + ß2 (PCTQ12)



22

If the argument is correct, then we would expect ß2 to be negative andsignificant: the larger the percentage of the low viewing quintile in theaudience, the smaller the increase in reported audience in the PPM results,compared with PMT. The results for model 1 are shown in table 4, wherePPM2+ = 13.659 + 1.146(PMT2+) – 5.661(PCTQ1).

Table 4SUMMARY RESULTS OF REGRESSION ANALYSIS FOR MODEL 1

t-value Significance

(Constant) 4.568 <.001

PMT2+ 148.865 <.001

PCTQ1 -.442 NS

The model fits well (R2 = .915, F<.001), but there is no evidence here tosupport the claim that light viewers are disadvantaged by PPM, compared toPMT. The sign for PCTQ1 is in the right direction (negative), but the result isnot significant.Model 2 used the proportion of quintile 1 and 2 as a measure of light viewers(PCTQ12). This model also fits well (R2 = .915, F<.001) and again, there is noevidence that light viewers are disadvantaged by PPM (table 5). The t valuefor the PCTQ12 variable is not significant, and is of the opposite sign thanpredicted. Similar analyses, for different sample subgroups failed to produceany support for the claim.

Table 5SUMMARY RESULTS OF REGRESSION ANALYSIS FOR MODEL 2

t-value Significance

(Constant) 3.452 .001

PMT2+ 149.364 <.001

PCTQ1 1.000 .317

We turn now to the competing claim, that the differences observed betweenthe results of our PMT panel and PPM panel are largely due to non-buttonpushing compliance in the PMT panel, corrected by the passive detection ofTV use by the PPM. We start with what we call “the household size”argument.



23

The difference between PPM and PMT PUT levels increases with householdsize: the larger the household the greater the difference between PPM and thepeople meter. However, by definition there is complete compliance in one-person people meter homes: all uncovered viewing is assigned to the oneperson in the home. Therefore, it can be argued, the PUT difference in largerhomes is simply due to a revealed non-compliance in people meter homes.This is illustrated in figure 8.

Figure 8AVERAGE MINUTE RATING FOR RESPONDENTS 2+ AND 18+ BY

HOUSEHOLD SIZE. MONDAY-SUNDAY 2:00-2:00, JAN 5-FEB 15 2004

26.9

23.2

15.3

13.312.7

26.6

23.5

16.4

14.9 15.4

27.6

23.5

24.9

17.8

19.3

27.6

23.5

25.4

18.0 18.4

0.0

5.0

10.0

15.0

20.0

25.0

30.0

HHS 1, 2+ HHS 2, 2+ HHS 3, 2+ HHS 4, 2+ HHS 5+, 2+ HHS 1, 18+ HHS 2, 18+ HHS 3, 18+ HHS 4, 18+ HHS 5, 18+

Sample subgroup

Aver

age

Min

ute

Ratin

g (%

)

PMT

PPM

Figure 8 shows the average minute PUT level by household size for allrespondents (2+) and for adults (18+). For both all persons 2+ and adults, thelevels are identical for one and two person homes; in larger homes PPM showshigher levels than PMT. Ergo, so the argument goes, the evidence for non-compliance in larger PMT homes. The relationship also holds for the 18-49group, where overall differences between PPM and PMT are greater; and italso holds just for households where all members of the PPM sample wereaccepted into tab (complete households). The relationship is therefore quiterobust.Supporting the argument is the fact that PPM compliance, as measured bymotion, is (almost) invariant by household size: there is no tendency for thosein larger households to show less motion in their PPMs than those in smaller



24

households. This, taken with the earlier evidence that there is no relationshipbetween viewing and motion (carry around) is a very powerful support for theargument that the culprit is PMT non-compliance in homes with more than oneperson.The difference in PUTS between PPM and PMT by household size may alsobe explained by PPM non-compliance, but the argument is much weaker. Theargument: those who plan not to view (or, maybe habitually light viewers) donot undock their PPMs. They therefore do not qualify and their real non-viewing (or light viewing) does not count in tabulation, thus explaining therelation between button pushing meters and PPM PUT levels by householdsize. There is (at least) one condition necessary for this to hold: those notundocking should live in larger households – i.e. there should be a negativecorrelation between response rate (as measured by in-tab/in-production) andhousehold size. We have not seen such a relationship: the PPM daily responserate is invariant by with household size.However, the interpretation of the household size difference as due to PPMnon-compliance (not undocking) is one explanation to a very puzzling PPMphenomenon: daily reach levels for PPM average around 98%-99% for alldemographic groups. Almost everyone accepted into the daily in-tab watchestelevision. This is at variance with both our people meter panel and ourtelevision diary studies. PMT daily reach levels are lower on average (88%)and vary more by demographic group from a low of about 83% for children toa high of 94% for the 50+. Diary daily reach levels are lower still.To some extent the high PPM reach levels could be due to its incorporation ofout of home viewing and to incidental viewing. But it could also be due, tosome extent, to PPM non-compliance: non-viewers do not undock their PPMs.We have seen that PPM audiences are, on average, 24% higher than those ofPMT for the total sample 2+. However, the PPM average rating for TV homesis about the same as that for PMT as shown in table 6. Here we see the averagePUT and HUT for PMT and for PPM for the whole day and for prime time.

Table 6COMPARISON OF AVERAGE PUTS AND HUTS FOR PPM AND PMT

PMT PPM Index

Individuals 2+ M-Su 2a-2a 18.0 22.3 1.24

Homes M-Su 2a-2a 29.9 30.3 1.01

Individuals 2+ M-Su 7p-11p 39.9 49 1.23

Homes M-Su 7p-11p 60.2 61 1.01



25

The data in table 6 implies that the increased viewing is due to an increase inthe average number of viewers per home – in other words, due to picking upthe viewing of second and third viewers. There is no tendency for this increaseto be skewed into different times of the day as figure 9 shows.

Figure 9AVERAGE VIEWERS (2+) PER HOUSEHOLD BY TIME BLOCK

JAN 5-FEB 15 2004

1.221.21

1.22

1.18

1.23

1.21

1.24

1.221.22

1.23

1.00

1.05

1.10

1.15

1.20

1.25

1.30

M-Su 2a-2a M-Su 7p-11p M-F 6a-12nn M-F 12n-4p M-F 4p-6p M-F 6p-7p M-Su 11p-2a M-F 2a-2a S+S 2a-2a Sa-Su 7a-7p

Time Block

Ratio

of P

PM:P

MT

On the face of it, this would seem to be strong evidence that the differencesbetween the two systems is due more to non-compliance in the PMT samplethan to non-cooperation in the PPM sample. However, we should point outthat the definition of a TV Homes rating in the PPM context is a little loose:unlike PMT, there is no guarantee that all people in a home are accepted intothe PPM in-tab. We do not necessarily have information on all viewers in ahome. Nonetheless, given the high in-tab rates of the PPM panel, there is someforce to the argument.If PPM is indeed “correcting” for non-compliance in the PMT world, then wewould expect it to show more evidence of casual viewing. That is, viewingwhere there is no particular incentive for a PMT panelist to push a button. Wenoted earlier that the variance of program ratings with PPM seems to be lessthan it is with PMT. There is a corollary. In comparing program audiences,PPM vs. PMT, we have been struck by the fact that highly targeted shows (e.g.



26

children’s shows, shows with a high percentage of older folk in the audience)seem to show a higher percentage of the audience “in the target” with PMTthan they do with PPM.This is illustrated in figure 10. It shows the distribution of the audience(audience composition) for the program “La Poule aux œufs d’or” according tothe two measurement systems. In the PMT system, the program attracts anaudience that is largely 50 years of age or older (69% of the total audience).Not surprising, since it is a quiz program, in its eleventh year and shown in theearly evening. However, according to the PPM system, the audiencecomposition is more diffuse: 54% of the audience is aged 50 or more with thedifference distributed among children and younger adults. The audience ratingfor the program increases among the 50+ crowd from 31% to 35%. The ratingamong younger adults (18-34) increases from 4% to 11%.

Figure 10AUDIENCE COMPOSITION FOR “LA POULE AUX OEUFS D’OR”

FOR PMT AND PPM. AVERAGED JAN 5-FEB 15 2004

0.9 1.12.2 3.0 2.8

21.0

24.1

44.9

3.55.5

3.3

5.7 6.2

28.8

21.6

25.4

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

C2-6 C7-11 T12-17 A18-24 A25-34 A35-49 A50-64 A65+

Age group

Perc

ent o

f tot

al (2

+) a

udie

nce

PMTPPM

This phenomenon is quite widespread and applies to programs that are tightlytargeted to children, to younger adults, to older adults, to men or to women. Inall cases, the variance of the audience composition is larger with PPM than it



27

is with PMT. One explanation is that PPM picks up “secondary” viewing lostby PMT. The thesis is that PPM will pick up viewing to programs by peoplewho have not personally chosen to view them – someone else in the home has– and has diligently pushed her button. PPM, because it is passive, will pick upviewing in these situations by second, third, etc., viewers who would not,perhaps, push their buttons in a PMT world because of its lesser importance tothem. So, programs that are quite “tightly” targeted in PMT become morediffuse in PPM: for example children’s programming where a parent orguardian is “in the same room” as the child, pushes the button for the child butnot for themselves, because it is not important to them.The argument is that this is due to the PPM technology being more apt to pickup casual unplanned viewing of a set that is being watched by some othermember of the family. The interpretation of the data in the above table is thatPPM is more likely to pick up the casual viewing activity of younger adults(and children or teens) when an older adult is the principal viewer of aprogram.We stated earlier that PPM generally yields higher estimates of televisionviewing, recently around 25% higher, but it also produces a differentdistribution of viewing. That is, light viewers (Quintile 1) view much moretelevision with PPM than with PMT; heavy viewers view about the sameamount of television with both measurement systems. Figure 11 shows theaverage minutes of television viewed during a one week period (February 9-15, 2004) for each quintile, according to the BBM PMT and PPM panels inQuébec francophone). A quintile analysis ranks panelists according to theamount of television viewed and forms five groups, from the lightest (lowestfifth) to the heaviest viewers (highest fifth). The analysis is done separately foreach measurement system (766 PMT panelists and 935 PPM panelists). SincePPM generally yields higher estimates of television viewing, we should expectthe average viewing to be higher in the PPM analysis than the PMT analysisfor each quintile – and it is. However, the difference is proportionately muchgreater, the lower the quintile (see figure 12).



28

Figure 11AVERAGE MINUTES OF TELEVISION VIEWED PER QUINTILE FOR PMT AND

PPM. AUDIENCE 2+, JAN 5-FEB 15 2004

55

129

206

313

569

101

190

266

351

584

0

100

200

300

400

500

600

700

Q1 Q2 Q3 Q4 Q5

Quintile (Light --> Heavy)

Aver

age

Min

utes

of T

elev

isio

n U

se.

PMT

PPM

Figure 12RATIO OF AVERAGE MINUTES VIEWED PER QUINTILE, PPM:PMT

1.84

1.47

1.29

1.12

1.03

1.00

1.10

1.20

1.30

1.40

1.50

1.60

1.70

1.80

1.90

Q1 Q2 Q3 Q4 Q5

Quintile

Ratio

of v

iew

ing,

PPM

:PM

T



29

PPM’s light viewers (quintile 1) watch, on average, 84% more television thanPMT’s light viewers. PPM’s heavy viewers (quintile 5) watch, on average, 3%more television than PMT’s heavy viewers. In other words, the overalldifference between the two systems is greater, the less the amount of viewing.So, light viewers pick up relatively more viewing with PPM than they do withPMT. The question is why? One hypothesis could be that it is just these lightviewers that are likely to be less compliant in pushing their buttons with PMT;with PPM, simply carrying the device around does the chore for them.

6. Summary: Why the differences?In summary, it is probable that both non-compliance arguments are, to someextent, valid: non-compliance in the people meter panel and the PPM panel areboth contributing to the difference in PUT levels. However, the balance ofevidence points to the major cause being under-reporting of casual viewing inthe PMT sample: 1) the difference is greater in larger households; 2) there ismore dispersion in the audience composition of programs with the PPM data;and 3) the lowest viewing quintile shows the greatest relative increase inreported audience. At the same time, we have been unable to demonstrate thata possible exclusion of more infrequent television viewers has any appreciableeffect on the results of the PPM surveys. We can, therefore, quantify thepossible reasons for the difference in audience estimates between the twosystems. Figure 13 illustrates our estimate of the weight (out of the 24percentage points) of each possible source for differences in the reportedaudiences between the push button PMT panel and the passive PPM panel.

Figure 13ESTIMATED IMPORTANCE OF DIFFERENT SOURCES OF DIFFERENCE

BETWEEN PPM AND PMT VIEWING ESTIMATES

��

2

3

1

5

11

2

Sample D iffs

O ut of Hom e V iew ing��Unmeasured sets

Incidental viewing

PMT non-compliance

PPM non-compliance



30

SUMMARY AND DISCUSSION

We have shown that the PPM system “works” and is reliable. Stations willencode their signals and the encoding works as advertised. Respondents willaccept our invitation to carry the device around, and they do for significantperiods of time, docking and undocking as instructed. The pattern of results isconsistent with those from a parallel push button meter system, although at ahigher absolute level (see also BBM Canada, 2004).The difference in the reported audience was examined from a number of frontsand we conclude that the largest contribution to the difference arises from non-compliance in the button-pushing panel. Although the exclusion of someviewing due to the carrying or motion compliance rule not being met isacknowledged as an issue, it is likely minor. Instead, we view the use of acompliance “report card” collected in the carry data on each respondent as a“reading” of our confidence that the PPM data adequately represents therespondent’s media day. This is unlike any other system we are familiar with,which implies that other systems systematically bias results to include datafrom respondents who do not represent their “true” media day.

ACKNOWLEDGEMENTS

The authors are grateful to Roberta McConochie, Bob Patchen, John Gill and Dan Amesfor their constructive comments on earlier drafts of this paper, and Randy Missen, FelipeCalderon and Dave Kelly for their research assistance.

FOOTNOTE

1. More information on the operation of the PPM may be found in Patchen andKolessar (1999) and Patchen and Webb (2002) and on the Arbitron website(http://www.arbitron.com/).

REFERENCES

Arbitron (2002). PPM Indirect Viewing Pilot Study Arbitron Research Standards &Practices Group, July.

BBM Canada (2004). Sound and Vision: Television audience measurement usingArbitron’s PPM. Edit rules, acceptance for commercialization criteria and extendedspecial analyses by BBM Canada.

Bendali, Abbas and Hugues Chavenon. (1995). What are People Doing while WatchingTV? ARF Global Media Research Workshop. New York, ARF.

Clancy, Maura (1992). How People Use Television. Proceedings of the WorldwideBroadcast Audience Symposium, Toronto 1992. Amsterdam, ESOMAR.



31

Kolessar, Ronald S. and Robert Patchen (1999). Taking PPM out of the Lab and into theField: a report on the Manchester (England) Pilot Test of the Personal Portable Meter.Proceedings of the Third ARF-ESOMAR Worldwide Radio Research Symposium.Amsterdam, ESOMAR.

Patchen. Robert H. and Beth M. Webb. (2002). The future is now: The very latestfindings from the U.S. market launch of the Portable People Meter in Philadelphia. ARF-ESOMAR WAM Proceedings.

Pellegrini, P.A. and Ken Purdye (2003). Panel fatigue: longitudinal and cross-sectionalapproaches to understanding time-in-panel effects, ARF-ESOMAR WAM Proceedings,Los Angeles.

Pellegrini, P.A. and Ken Purdye. (2002). Pushing picture matching to the limit: Canada’sfour year adventure. ARF-ESOMAR WAM Proceedings, Cannes.

Rosen, Marcella (1994). Out of Home Television Viewing: the Invisible Audience.Proceedings of the Worldwide Electronic Media and Broadcast Symposium, Paris, 1994.Amsterdam, ESOMAR

Stipp, Horst and Julian Pounds (1994). New Research on the Out of Home TelevisionAudience in the U.S. and Europe. Proceedings of the Worldwide Electronic Media andBroadcast Symposium, Paris, 1994. Amsterdam, ESOMAR

THE AUTHORS

Pasquale (Pat) A. Pellegrini is Vice-President Research, BBM Canada, Canada.

Ken Purdye is Meter Consultant, BBM Canada, Canada.

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Documents

A comprehensive comparison from parallel TV ... - cb-cda.gc.ca · existing PMT panel, where no re-processing is required and the next day’s estimates are also the final estimates