A Physical Therapist Is Interested in Whether People with Different

Multiple Choice

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 (X_S) and large-boned frame (X_L) .Patients all had similar injuries.She measures the number of days each person takes to progress to a predetermined point.Here is the data:
What is the estimated standard error of the difference?

A) 1.13
B) 1.28
C) 1.63
D) 3.30