Subject Variables:
 want to include representative sample of individual differences
 want sample to generalize to population
 create a selection criteria
 carefully choose criteria to avoid bias
Sampling Techniques:
 simple random sampling
 i.e., draw from hat
 systematic random sampling
 i.e., every other name
 limitations exist
 often topic limits, subjects unavailable
Sample Size:
 N=population, n=sample
 larger=more representative of populaton
 larger=more likely to include all relevant subject variables
 in laboratory, N=100, n=30
 vulnerable to volunteer bias, mortality, sophistication
Controlling Subject Variables:
 betweensubject
 withinsubject
 random assignment, counterbalancing, limit population
 matched groups
 repeated measures, pre/posttest
