Gain Score ?Measurement IssuesCeiling effect Skewness Reliability issue

Statistical IssuesIndependence Sample size Standard error Type II error ( null hypothesis is false but fail to reject) Statistical Power (the probability of correctly rejecting null hypothesis) (increase sample size, increase effect size, increase alpha decrease variance/standard deviation) Equivalent control group or non-equivalent control group Statistical control ANCOVA (adjust the post-test score for the measured pretest

scores or removes pretest differences between the treatment and control group)

Research Design IssuesExperimental / quasi-experimental design Sample size Standard error Control Extraneous factors

Solutions? posttest score, ANCOVA, Repeated Measures