26 terms

Chapter 7: Sampling

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bias sample
Some members of the pop. of interest are more likely to be included in the sample
representative sample
All members of the population have an equal chance of being included in the sample
self-selection sampling (biased)
Sample has only people who volunteered to participate
cluster sampling (prob)
Clusters of participants w/i a population are randomly selected and all members are used
multistage sampling (prob)
2 random samples are selected: a random sample of clusters, then a random sample of people w/i the cluster
stratified random sampling (prob)
Researchers select demographic categories to represent % in population and uses random selection
oversampling (prob)
Researcher intentionally overrepresents one or more groups
oversampling (prob)
Researcher decides that 4% of the population isn't enough to be representative, so they sample 10%
systematic sampling (prob)
Researcher uses a computer or a random number table to select 2 random numbers
self-selected, convenience, snowball, purposive, quota
What are the 5 types of non-probability samples?
snowball sampling (biased)
Researchers find rare individuals and ask participants to bring friends (hard-to-access population)
quota sampling (biased)
Researcher identifies subsets in the population and sets a target number for each category
(80 African Americans, 80 Latinos)
random sampling
What is most important for enhancing external validity?
1,000
What sample size is often cited as the optimal balance between accuracy and effort?
simple random, systematic, stratified, cluster, oversample, multistage sampling
What are the 6 types of probability sampling?
purposive sampling (biased)
If researchers want to study only certain kinds of people, they recruit only those participants
frequency claim
Typically, in which type of claim is it most important to have a random sample?
sampling error (random error)
No 2 samples will be the same; there's always variation
sample bias (random error)
Sample is systematically bias
Increase sample size, estimate using stats
How can you reduce sampling error?
sample bias (constant error)
Selected based on ease or any other systematic difference (self-selection)
sample isn't representative
Why does sample bias reduce external validity?
simple random sampling (prob)
Identify all members of the pop & randomly sample
high external validity
If you conduct a study w/i representative sample, you have...
oversampling
In which type of sampling
do researchers adjust final results?
systematic sampling
Researcher starts with the 4th person and then count off every 7th person
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