What is the difference between a main effect and an interaction effect?

Order Instructions

Consider factors associated with behavioral sciences research. Cite references from your textbook or other scholarly sources to support your response. Respond to the following in a minimum of 175 words:

What is the difference between a main effect and an interaction effect?

What is the difference between a longitudinal, cross-sectional, and sequential research design?

Read the case studies and answer the questions that follow. Add your answers to the final part of your response:

Case Study 1:

A researcher is investigating verbal behavior among introverts and extroverts. The researcher first tests participants and classifies them as either introverted or extroverted. She then randomly assigns participants to a high anxiety or a low anxiety social group and observes the number of words spoken by participants. The researcher wants to learn more about the effects of both personality style—introversion or extroversion—and social situation—high or low anxiety—on verbal behavior. In this case, verbal behavior is defined as the number of verbal communications uttered within a 5-minute observation period.

What type of design is this? Provide an example of a possible main effect that might emerge from this study. Additionally, provide an example of a possible interaction that might emerge.

Case Study 2:

A researcher is investigating the effects of life-review group therapy on depression among elderly residents of assisted care facilities. The researcher identifies 2 facilities and recruits volunteer participants. In one of the facilities, life-review therapy is conducted for 8 weeks. In the other facility, a no-treatment support group takes place for 8 weeks. Depression is measured after the program is administered.

What type of research design is this? What is the greatest threat to internal validity in this type of design? Explain.