Dr. Phan conducted an experiment to see whether taking breaks at work improved employee motivation. Although the employees in the "take more breaks" condition did report higher motivation on average, Dr. Phan became concerned when he saw that several employees in the "do not take breaks" condition never finished his study. Which of the following threats to internal validity would Dr. Phan be most worried about? a. A mortlity (attrition) effect b. A maturation effect c. An instrumentation effect d. A lack of generalizability (external validity) Why do researchers often need to collect data from many different individuals in their population of interest when they are sampling participants for their study? a. To increase the odds of finding a positive result b. To increase the precision with which population-level parameters are estimated c. To determine what population is being studied d. To answer the research question using the highest possible unit of analysis While designing her next research project, Dr. Petrov decided to use a mixed-methods study design. Which of the following justifications would she be most likely to give if someone asked her about this preference? a. "I can finish my data collection earlier by taking advantage of many different data sources; and can therefore get my research out to the public sooner." b. "This will allow me to make sure that every variable in my study is assessed at the most appropriate unit of analysis." c. "I can study my variables in a way that combines multiple different perspectives and minimizes the bias of any single design type." d. "I want to maximize the external validity of my study, so I don't want to cause too much interference by using only a single method." A researcher conducts a cross-sectional study, and concludes that their two variables seem to be related. However, the researcher ultimately wants to establish whether there is a cause-and-effect relationship between those variables. A longitudinal study would satisfy the conditions needed to establish a cause-effect relation. Select one: True False