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Group Name: ________________________
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Random Sampling Methods
Key Understanding: every member is equally likely to be chosen
Simple Random Sampling – Use a random number generator or a random number table to
determine which members are chosen.
Cluster Sampling – Population is divided into clusters reflecting the variability within population and then a certain number of
clusters are randomly selected and every member of the selected cluster is surveyed.
Systematic Sampling – Sampling every k th member of a population after randomly determining the first individual by
selecting a random number between 1 and k.
Stratified Random Sampling – The population is divided into two or more groups (strata) according to some criterion and
subsamples are randomly chosen from each strata.
Identify the type of sampling used in each of the following vignettes and explain your choice:
1.
Ohio wants to gauge public reaction to a proposed tax increase. They randomly select individuals from rural areas,
randomly select individuals from suburban areas, and randomly select individuals from urban areas.
Type of sampling: stratified
Explain:
The population is divided into 3 groups: rural, suburban, and urban
Sample is randomly selected from each group.
2.
Bauman’s Orchard wants to determine the approximate yield of its peach trees. They divide the orchard into 25
subsections and randomly select 4. They sample all the trees within the 4 subsections to approximate the yield of the
orchard. Type of sampling: Cluster
Explain:
The population was divided into subsections (clusters).
4 subsections (clusters) are randomly selected from the 25 and then each member of each subsection is
chosen for inclusion in the sample.
3.
Every hundredth hamburger manufactured is checked to determine its fat content.
Type of sampling: Not Random Sampling but has potential to be systematic
Explain:
If the first hamburger tested was randomly selected from 1 to 100 and then every 100 th hamburger
thereafter was tested it would be systematic RS. So if a random number generator gave 15 as the start
number, a systematic method would test hamburgers 15, 115, 215, 315, etc.
4.
Design consultants are selected using random numbers in order to determine annual salaries.
Type of sampling: Simple random sampling
Explain:
Using a random number generator gives each member of the population equal chance to be chosen.
5.
A survey regarding download time on a certain web site is administered on the internet by a market research firm to
anyone who is willing to respond to the survey. Type of sampling: Not random sampling
This is sometimes called volunteer sampling but it is not a random sampling method
Explain:
Volunteers who answer surveys usually have strong opinions and would bias the sample. This is not a
random sampling method.
Table Number:__________
Group Members:____________ANSWER KEY
Group Name: ________________________
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