1. Sample Selection Issues in Experiment Random sampling (difficult) Convenience & purposive sampling Volunteers External validity Representativeness & generalizability Selection bias

2. Allocation Methods Unrestricted random allocation Cluster randomization Restricted random allocation Stratified randomization Random permuted blocks Minimization Simple cross-over (Latin square)

3. Group Design Methods Solomon four group method Two experimental and control groups, one group w/ pre-test and the other one w/o pretest Control for reactive effect of pre-testing Complete factorial experiment More than one experimental or control groups Examine possible interaction between independent variables or dosage effect.

4. Controlling Methods Matching Precision control (matching pairs) Frequency distribution control Adjustments in analyses Statistical techniques cross-tabulation Standardization regression