Hip replacement (total hip arthroplasty) is surgery to replace a worn-out or damaged hip
joint. The surgeon replaces the old joint with an artificial joint (prosthesis). This surgery
may be a choice after a hip fracture or for severe pain because of arthritis.
A medical center developed a new surgical procedure designed to reduce the average
recovery time from hip surgery. To test the effectiveness of the new procedure, a study
was conducted in which 224 patients needing hip replacement surgery were randomly
assigned to receive either the standard procedure or the new procedure.
Summary statistics on the recovery times from the surgery are shown in the table.
Type of Procedure
Standard
New
Mean Recovery Time Standard Deviation
Sample Size
(days)
Recovery Time (days)
110
114
38
12.3
35
10.9
Complete a significance test to determine if the data provide convincing statistical
evidence that
those who receive the new procedure will have less recovery time from the
surgery
on average, than those who receive the standard procedure for patients similar to
those in the study.