How can a researcher improve internal and external validityS

Solution

In group research, the primary methods used to achieve internal and external validity are randomization, the use of a research design and statistical analysis that are appropriate to the types of data collected, and the question(s) the investigator(s) is trying to answer. Single-subject experimental studies almost always have high internal validity because subjects serve as their own controls but, as mentioned earlier, are extremely low with respect to external validity. Single-subject studies acquire external validity through the process of replication and extension (i.e., repeating the study in different settings, with a different subject, etc.). The results of group studies are also more acceptable by the scientific community when replicated.