Probability
all members of the population have an equal probability of being included.
Unbiased sample (representative sample)
not all members of a population have an equal probability of being included
Biased Sample (unrepresentative sample)
What is the most common sampling technique in behavioral research?
convenience sampling
The entire set of people or things in which you are interested;
Population
Sampling only those who volunteer
Self-selection
Clusters of participants within a population of interest are randomly selected, and then all individuals in each selected cluster are used.
Cluster sampling
samples that are easy to access; this is a common technique in behavioral research.
Convenience sampling
If a sample is biased, then it is ________ of the population of interest.
unrepresentative
a smaller set of people or things that is taken from the population
Sample
“pulling names from a hat”
Simple random sampling
Two random samples are collected
•Stage 1: A random sample of clusters is selected from your population of interest.
•Stage 2: From those selected clusters, a random sample of people is chosen.
Multistage sampling
used when you want to study certain kinds of people, so you only recruit those types of participants.
Purposive sampling
Online surveys commonly suffer from which threat to external validity?
self-selection
If you sample every member of the population then you are conducting a ______.
Census
In a frequency claim, _______ validity is a priority.
external
A multistage technique in which the researcher selects specific demographic categories (such as race or gender) and then randomly selects individuals from each of the categories.
Stratified random sampling
a variation on purposive sampling in which participants are asked to recommend other participants for the study.
Snowball sampling
A sample is to ________ as a population is to ________.
part; entire
Random ________
Increases external validity
sampling
Sampling_______, not sample ____, determines external validity.
technique; size
a variation of stratified random sampling in which a researcher over represents one or more groups.
Oversampling
similar to stratified random sampling; the researcher identifies subsets of the population and then sets a target number (i.e., a quota) for each category in the sample. Then she uses nonrandom sampling until the quotas are filled.
Quota sampling
Sanchez conducts a simple random sample of 500 men who became fathers for the first time in the past year. He finds that 23% of them report being unsure of their ability to be good fathers, plus or minus 4%. What is another term for the 4% value?
Margin of Error
Random ________ : used only in experimental designs
–Increases internal validity
assignment
EX: roll two dice. Let’s say one lands on 5 and the other lands on 3. I would start at the 5th person in the class and then choose every 3rd person.
Systematic sampling