At a large academic medical center, an analyst is understanding how patient characteristics translate to the length of stay of a patient. He collects a sample of 75 recent surgeries. Each observation consists of a variable NumSurgeryCPT (the number of surgical current procedural terminology (CPT) codes; essentially, the number of surgical procedures); the variable BMI (the body mass index of the patient); the variable CaseMinutes (the duration of surgery in minutes); and the variable LengthOfStay (the number of days the patient spent in the hospital). The analyst runs a regression of LengthOfStay on NumSurgeryCPT, BMI and CaseMinutes, and obtains the following regression:

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