Marks: 2 A physical therapist is interested in whether people with different bone structures will be affected differently by her new therapy program. She randomly chooses two groups of patients based on bone type: small-boned frame (XS) and large-boned frame (XL). Patients all had similar injuries. She measures the number of days each person takes to progress to a predetermined point. Here is the data: Small Bones Large Bones Mean 10.00 12.00 n 15 12 s2 4.5 5.0 SS 108 105 What is the pooled variance estimate?