A researcher conducted a study to determine the factors that predict pain intensity in patients with knee osteoarthritis. Before conducting the multiple regression, he found that the percentage of muscle tissues in the legs, the percentage of fat tissues in the legs, age, and gender correlated with pain intensity. He also found that percentage of muscle tissues in the legs and the percentage of fat tissues in the legs were strongly correlated. What a potential issue the researcher may face if he used all four predictors in the regression model? And explain one test that is used to assess this issue?

4. An example of the use of goodness of fit test in a known distribution that is not 50:50 is the investigation of how common venous thromboembolism with certain blood types. Mention another example of a variable that has known distribution?