Gain Score In Data Analysis

Gain Score ? Measurement Issues Ceiling effect  Skewness  Reliability issue 

Statistical Issues Independence  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 –α 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 Issues Experimental / quasi-experimental design  Sample size  Standard error  Control  Extraneous factors 

Solutions? – posttest score, ANCOVA, Repeated Measures