An article in Knee Surgery Sports Traumatology Arthroscopy 2

An article in Knee Surgery, Sports Traumatology, Arthroscopy (2005, Vol. 13, pp. 273-279), considered arthroscopic meniscal repair with an absorbable screw. Results showed that for tears greater than 25 millimeters, 14 of 19 (74%) repairs were successful while for shorter tears, 22 of 31 (71%) repairs were successful. (a) Is there evidence that the success rate is greater for longer tears? Use Alpha= 0.05 . What is the P-value? (b) Calculate a one-sided 95% confidence bound on the difference in proportions that can be used to answer the question in part (a). (a) Then is not evidence that the success rate is greater for longer tears. The P-value is 0.4051 Round your answer to four decimal places (e.g. 98.7654).

Solution

It is a right-tailed test.

The test statisitc is

Z=(phat-p)/sqrt(p*(1-p)/n)

=(0.74-0.71)/sqrt(0.74*(1-0.74)/19+0.71*(1-0.71)/31)

=0.23

So the p-value= P(Z>0.23) =0.4090 (from standard normal table)