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Introduction of StatisticIntroduction of Statistic

and Data Collectionand Data Collection

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Why a Manager Needs to KnowWhy a Manager Needs to Know

About Statistic?About Statistic?Managers needs an understanding ofManagers needs an understanding of

statistics for the following four keystatistics for the following four keyreasons:reasons:

To know how to properly present andTo know how to properly present and

describe informationdescribe information To know how to draw conclusions aboutTo know how to draw conclusions about

large population based only on informationlarge population based only on informationobtained from samplesobtained from samples

To know how to improve processesTo know how to improve processes

To know how to obtain reliable forecastsTo know how to obtain reliable forecasts

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The Growth and Development ofThe Growth and Development of

Modern StatisticsModern StatisticsHistorically, the growth and developmentHistorically, the growth and development

of modern statistics can be traced toof modern statistics can be traced tothree separate phenomena;three separate phenomena;

1.1. The needs of government to collect dataThe needs of government to collect dataon its citizenryon its citizenry

2.2. The development of the mathematics ofThe development of the mathematics of

probability theoryprobability theory

3.3. The evolution of electronic computingThe evolution of electronic computing

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KeyKey DDefinitionsefinitions

A population (or universe) is the totality ofA population (or universe) is the totality ofitems or things under consideration.items or things under consideration.

A parameter is a summary measure thatA parameter is a summary measure thatdescribes a characteristic of an entiredescribes a characteristic of an entirepopulation.population.

A sample is the portion of the populationA sample is the portion of the populationthat is selected for analysis.that is selected for analysis.

A statistic is a summary measureA statistic is a summary measurecomputed from sample data that is used tocomputed from sample data that is used todescribe or estimate a characteristic of thedescribe or estimate a characteristic of the

entire population.entire population.

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Descriptive versusDescriptive versus IInferentialnferential

SStatisticstatistics Descriptive statistics are methods thatDescriptive statistics are methods that

focus on the collection, presentation, andfocus on the collection, presentation, andcharacterization of a set of data in order tocharacterization of a set of data in order to

properly describe the various features ofproperly describe the various features of

that set.that set.

Inferensial statistics make possible theInferensial statistics make possible the

estimation of a characteristic of aestimation of a characteristic of apopulation or the making of a decisionpopulation or the making of a decision

concerning a population based only onconcerning a population based only onsample results.sample results.

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Why data are neededWhy data are needed

Reason for Obtaining Data:Reason for Obtaining Data:

1.1. Data are needed to provide the necessary inputData are needed to provide the necessary input

to a surveyto a survey2.2. Data are needed to provide the necessary inputData are needed to provide the necessary input

to a studyto a study

3.3. Data are needed to measure performance of anData are needed to measure performance of anongoing service or production processongoing service or production process

4.4. Data are needed to evaluate conformance toData are needed to evaluate conformance to

standardsstandards5.5. Data are needed to assit in formulatingData are needed to assit in formulating

alternative courses of action in a decision makingalternative courses of action in a decision making

process.process.6.6. Data are needed to satisfy our curiosity.Data are needed to satisfy our curiosity.

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Types of data and their sourcesTypes of data and their sources

Data Type Question Types Responses

Categorical

Numerical

Do you currently own stock or bonds?

Discrete

Continuous

To how many magazinesDo you currently subcribe?

How tall are you?

Yes No

Number

Inches

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Data collectors are labeledData collectors are labeled primaryprimarysourcessources; data compilers are called; data compilers are called

secondary sourcessecondary sources..There are four method for dataThere are four method for datacollection:collection:

1.1. Government, industrial, or individualGovernment, industrial, or individualsourcessources

2.2. ExperimentationExperimentation3.3. SurveysSurveys

4.4. Observational studyObservational study

Types of data and their sourcesTypes of data and their sources

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Design ofDesign of SSurveyurvey RResearchesearch

1.1. Based on the reason:Based on the reason:•• Basic research Basic research 

•• Applied Research Applied Research 

2.2. Based on the purpose:Based on the purpose:•• Deskriptive Deskriptive Research Research 

•• Explanation Research Explanation Research 

•• Exploratory Research Exploratory Research 

3.3. Based on the place:Based on the place:•• Library Research Library Research 

•• Laboratory Research Laboratory Research 

•• Field Research Field Research 

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Types ofTypes of SSamplingampling MMethodsethods

There are three main reasons forThere are three main reasons for

drawing a sample;drawing a sample;1.1. A sample is less timeA sample is less time--consuming than aconsuming than a

census.census.

2.2. A sample is less costly to administer thanA sample is less costly to administer than

a census.a census.

3.3. A sample is less cumbersome and moreA sample is less cumbersome and morepractical to administer than a census.practical to administer than a census.

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Types ofTypes of SSamplingampling MMethodsethods

Types of Samples Used

Nonprobability Samples Probability Samples

JudgmentSample QuotaSample Chunk

Simple

RandomSample

SystematicSample StratifiedSample ClusterSample

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Types ofTypes of SSurveyurvey EErrorsrrors

Coverage ErrorCoverage Error occurs if certain groupsoccurs if certain groups

of subjects are excluded from this frameof subjects are excluded from this framelisting so that they have no chance oflisting so that they have no chance of

being selected in the sample. Coveragebeing selected in the sample. Coverage

error results in aerror results in a selection biasselection bias.. Nonresponse ErrorNonresponse Error arises from thearises from the

failure to collect data on all subjects in thefailure to collect data on all subjects in thesample and results in asample and results in a nonresponsenonresponse

biasbias..

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Sampling ErrorSampling Error reflects the heterogenity, orreflects the heterogenity, or

““chance differenceschance differences””, from sample to sample, from sample to sample

based on the probability of particular individualsbased on the probability of particular individualsor items being selected in the particularor items being selected in the particular

samples. Sampling error can be reduced bysamples. Sampling error can be reduced by

taking larger sample sizes, although this alsotaking larger sample sizes, although this alsoincreases the cost of conducting the survey.increases the cost of conducting the survey.

Measurement Error; obtaining meaningfulMeasurement Error; obtaining meaningful

measurements is often easier said than done.measurements is often easier said than done.There are three sources of measurement error:There are three sources of measurement error:

ambiguous wording of questions, the halo effect,ambiguous wording of questions, the halo effect,

and respondent error.and respondent error.

Types ofTypes of SSurveyurvey EErrorsrrors

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Ethical Issues. Measurement errorEthical Issues. Measurement error

becomes an ethical issue in one of threebecomes an ethical issue in one of threeways:ways:

1.1. A survey sponsor may purposely choose loaded,A survey sponsor may purposely choose loaded,

leadlead--in question that would guide the responsesin question that would guide the responsesin a particular direction.in a particular direction.

2.2. An interviewer, through mannerisms and tone,An interviewer, through mannerisms and tone,

may purposely create a halo effect or otherwisemay purposely create a halo effect or otherwiseguide the responses in a particular direction.guide the responses in a particular direction.

3.3. A respondent having disdain for the surveyA respondent having disdain for the survey

process may willfully provide false information.process may willfully provide false information.

Types ofTypes of SSurveyurvey EErrorsrrors