1. The document discusses internal and external validity as criteria for evaluating research designs. 2. Internal validity refers to how well a study establishes that changes in the dependent variable are caused by the independent variable rather than other factors. Threats to internal validity include history, maturation, pretesting, and more. Random assignment, matching, and other techniques can help control for threats. 3. External validity concerns the generalizability of findings to other populations, settings, variables, and measures. Types of external validity include population, ecological, and validity of operations.