Would it be appropriate to use these results to predict the length of stay for female patients over age 60 admitted with hip fractures? Why or why not?

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.