A study was conducted to examine gallbladder function before and after a surgical procedure designed to stop stomach contents from flowing back into the esophagus in patients with gastroesophageal reflux disease. The primary outcome was a measurement called gallbladder ejection fraction (GEF), which is a continuous outcome that reflects gallbladder function. The goal of the surgery is to increase GEF. Using a 5% significance level, test the claim that surgery increases mean gallbladder ejection fraction. Define_das the mean of the differences defined as d = postsurgical GEF - presurgical GEF, and assume normality of the distribution of the differences.

The mean of the post - pre differences for 15 patients was 18.075, and the corresponding standard deviation was 32.68.

30. What are the null and alternative hypotheses?

31.What is the critical value for the test?

32. What is the value of the test statistic?

33. What conclusion should you make based on the given data?