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
