If these researchers had already established that a causative relationship existed between these variables and asked you for a statistics consultation, what would you tell them is the appropriate regression technique to apply? Explain your answer.

In another study, researchers randomly selected five hospitals with orthopedic units in the United States and collected data from all the male patients over age 60 admitted for hip fracture. The researchers then report that admission levels of creatinine and hemoglobin can be used to predict the number of days the patient will need to stay in the hospital.