Threats to Internal Validity

To determine whether there are gender differences in knowledge about political issues, a psychologist stops people on the street, and asks them to take a survey on political issues. She finds that women know more about politics than men do. A potential threat to interval validity is

• Selection of Subjects

• Selection by Maturation

• Regression to the Mean

• Instrumentation Threat

Children recently enrolled at a nursery school are having trouble adjusting. The head teacher designs a story telling program to help them adjust. Four weeks later, observations are made and the children are better adjusted than they were before the program began. A potential threat to internal validity is:

• Instrumentation Threat

• Testing Threat

• Maturation

• Regression to the Mean

A math test is given to incoming first-year college students. Those scoring the lowest are selected for a 1-week math enrichment program. Following participation, students are tested again and their scores have improved. Credit for this change is given to the program. A potential threat to interval validity is:

• Regression to the Mean

• Selection by Maturation

• History Threats

• Instrumentation Threat