P7 Sampling Techniques.ppt

7/28/2019 P7 Sampling Techniques.ppt

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SAMPLING TECHNIQUES

PROBABILITY SAMPLING: Drawing a sample that is

statistically representative of the target population.

STEP 1: Identify target population.

STEP 2: Construct the sampling frame such that allpopulation elements have a known, non-zeroprobability of being selected.

STEP 3: Select the random sampling procedure bestsuited for the study.

Random Sampling Procedures

A) SIMPLE RANDOM SAMPLE: Sample points are randomlyselected from the sampling frame.

1) Each population element is included in an electronic file.

2) Sample points are selected randomly by a computer

program.


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B) SYSTEMATIC RANDOM SAMPLE: Sample points are spread

over entire sampling frame.

1) Determine the sampling interval N/nwhere N = population size;

n = sample size

e.g., N = 8000 and n = 200 N/n = 8000/200 = 40

2) Determine one random number (k) in the first interval.

e.g., k = 12

3) The sample contains the kth element in each sampling

interval.i.e., 1st interval12th element

2nd interval12 + 40 = 52nd element

3rd interval12 + 80 = 92nd element

4th interval 12 + 120 = 132ndelement

200th

interval 12 + 7960 = 7072nd

element


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C) STRATIFIED RANDOM SAMPLE: Sample points are

proportionally represented within population subgroups. The

subgroups are chosen with the needs of the study in mind.

e.g., N = 8000 and n = 200

Male = 43% and Female = 57%

.43 x n = .43 x 200 = 86 males

+ .57 x n = .57 x 200 = 114 females

n = 200


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D) CLUSTER SAMPLING: : Sample points are all the members of

a naturally occurring unit (cluster).

1) The target population is divided into natural occurring

subgroups (clusters).

e.g., UW-Ls 19 sports clubs

2) Subgroups are randomly chosen.

e.g., AIKIDO CLUB, CYCLING CLUB, EQUESTRIAN CLUB,

RUGBY CLUB (WOMEN'S), VOLLEYBALL CLUB (MEN'S)

3) Sample points are all elements in chosen clusters.


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SAMPLING TECHNIQUES

NON- PROBABILITY SAMPLING: Drawing a sample of a

hard-to-identify group for which a sampling frame is notavailable.

1) CHUNK SAMPLING (INTERCEPT SURVEY): Go to the

location where you will find people who are members ofthehard-to-identify group.

2) JUDGMENT SAMPLING: Hand pick the respondents.

3) CONVENIENCE SAMPLING: Survey anyone.


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NOTES: When a non-probability sampling procedure is used:

1) the reasons for choosing the non-probability sampling

procedure and the limitations of the sampling procedure

must be explained in the report.

2) efforts to introduce variation in the sampling proceduremust be explained in the report.

3) statistical inferences can not be made unless the

assumption is made that the sample is random. This

assumption must be explained in the report.

Non-Random Sampling Procedures


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Things You Should Know

1. Exam 1 is on Monday/Tuesday of next week. Information

about exam 1 is on the web site in Exam 1 Memo

2. Teams surveying UW-L students:

a. Submit your request for a sample to me in classtomorrow.

b. Its time to learn about Select Survey

c. You will be emailed your sample and Select Survey

login information later this week.
http://www.uwlax.edu/faculty/sherony/bus230/Handouts/Exam%201%20Memo.pdfhttp://www.uwlax.edu/faculty/sherony/bus230/selectsurvey.htmhttp://www.uwlax.edu/faculty/sherony/bus230/selectsurvey.htmhttp://www.uwlax.edu/faculty/sherony/bus230/Handouts/Exam%201%20Memo.pdf

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P7 Sampling Techniques.ppt