Which of the following can be a threat to the internal validity of a study?
Only history effects
Only regression toward the mean
Only regression toward the mean and heterogencous attrition
History effects, regression toward the mean, and heterogeneous attrition
Which of the following can be a threat to the internal validity of a study?
O Only history effects
O Only regression toward the mean
O Only regression toward the mean and heterogencous attrition
O History effects,regression toward the mean,and heterogencous attrition