For each description below, indicate if it is an issue with internal validity, external validity, or reliability: Subjects in a study complete a task in the lab in a different way than they would...

For each description below, indicate if it is an issue with internal validity, external validity, or reliability: Subjects in a study complete a task in the lab in a different way than they would ordinarily do it. Subjects’ scores on a mood questionnaire differ each time they complete the questionnaire. Different groups of subjects receive different teaching techniques to compare the effectiveness of the techniques on learning. However, the subjects in the different groups also differ in their pre-existing knowledge of the topic being taught.