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Ch. 16 SAMPLING DESIGNS

AND SAMPLING PROCEDURES

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Dr. Werner R. Murhadi

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Sampling Terminology

Sample is a subset, or some part, of a larger population.

population (universe) is any complete group of entities that share

some common set of characteristics.

population element is an individual member of a population.

Census is an investigation of all the individual elements that make up a

population.

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Why Sample?

Pragmatic Reason: Applied

business research projects

usually have budget and time

constraints.

Accurate and Reliable

Results: see figure

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Practical Sampling Concepts

sampling frame

A list of elements from which a

sample may be drawn; also

called working population.

sampling unit

A single element or group of

elements subject to selection in

the sample.

LOGORandom Sampling and

Nonsampling Errors

Random sampling error is The difference between the

sample result and the result of a census conducted using

identical procedures.

Random sampling error is a function of sample size. As

sample size increases, random sampling error

decreases.

Systematic (nonsampling) errors result from

onsampling factors, primarily the nature of a study’s

design and the correctness of execution.

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Total Error

Random Sampling Error,

occur because the particular

sample selected is an

imperfect representation

of the population of interest

Nonsampling Error

Response Error Nonresponse Error

Researcher Error Interviewer Error Respondent Error

Surrogate Information Error

Measurement Error

Population Definition Error

Sampling Frame error

Data Analysis error

Respondent Selection Error

Questioning Error

Recording Error

Cheating error

Inability Error

Unwillingness Error

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Sampling frame errors eliminate some potential respondents.

Random sampling error (due exclusively to random, chance

fluctuation) may cause an imbalance in the representativeness of

the group.

Additional errors will occur if individuals refuse to be interviewed

or cannot be contacted.

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Nonprobability Sampling

probability sampling is A sampling technique in which

every member of the population has a known, nonzero

probability of selection.

nonprobability sampling is A sampling technique in

which units of the sample are selected on the basis of

personal judgment or convenience; the probability of any

particular member of the population being chosen is

unknown.

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Sampling technique

Nonprobability Probability

Convenience/

Haphazard/

Accidental

Judgmental/

Purposive

Quota Snowball

Simple Random Systematic Stratified Cluster Others

Proportionate Disproportionate

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Convenience Sampling

Also called haphazard or accidental

sampling

The sampling procedure of obtaining

the people or units that are most

conveniently available (people passing

in a mall).

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Judgment Sampling

Also called purposive sampling

An experienced individual selects the

sample based on his or her judgment

about some appropriate characteristics

required of the sample member (CPI

Consumer Price Index).

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Quota Sampling

Ensures that the various subgroups in

a population are represented on

pertinent sample characteristics (Brand

of DVD owners ie. Sony, Samsung,

Toshiba )

To the exact extent that the

investigators desire

It should not be confused with stratified

sampling.

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Snowball Sampling

A variety of procedures

Initial respondents are selected by

probability methods

Additional respondents are obtained

from information provided by the initial

respondents (Buyers of more than 50

DVDs per year).

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Simple Random Sampling

A sampling procedure that ensures that

each element in the population will have

an equal chance of being included in

the sample (Lottery)

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Systematic Sampling

A simple process

Initial random point

Every n-th name from the list will be

drawn

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Stratified Sampling

Probability subsample in each strata

Subsamples are drawn within different

strata or groups

Each stratum is more or less equal on

some characteristic

Do not confuse with quota sample

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Cluster Sampling

The purpose of cluster sampling is to

sample economically while retaining the

characteristics of a probability sample.

The primary sampling unit is no longer

the individual element in the population

(ie. Cities, universities, career)

The primary sampling unit is a larger

cluster of elements located in proximity

to one another

LOGOWhat is the

Appropriate Sample Design?

Degree of accuracy

Resources

Time

Advanced knowledge of the population

National versus local

Need for statistical analysis

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