STATISTICS

A study published in JAMA in 2004 examined past results of other studies on bariatric surgery. Bariatric surgery is done to replace the size of the stomach in various ways. It is typically used on only obese patients, and one the traditional form of the surgery, gastric bypass has a 1% mortality (death) rate caused by the surgery. However, in the studies reporting on the effects of this surgery on Type II diabetes, 1417 of 1846 diabetic patients recovered completely from diabetes after surgery. These patients no longer need medication like insulin (which is injected into the skin) or pills to help manage blood sugar.

(a) What is the percentage of patients who recovered from diabetes in 2004?

(b) What is the 90%, 95% and 99% Confidence Interval for the percentage of recovery from diabetes (2004) data? (to four decimal places for the proportion - two decimal places if you give your answer as a percentage).

In a study released a decade later, the percentage of patients who recover from diabetes has increased to 80%. Using Confidence Intervals determine whether this is a significant change from the 2004 data.  Use n=2000

(c) What is the percentage of patients who recovered from diabetes in 2014?  What is the number of patients in the sample that have recovered?

(d) What is the 90%, 95% and 99% Confidence Interval for the percentage of recovery from diabetes (2014) data? (to four decimal places for the proportion - two decimal places if you give your answer as a percentage).

(e) Based on a comparison of the confidence intervals (compare only using the 95% confidence interval) do you think that the data suggests a significant change in the number of people who have recovered from Diabetes?  Why? Why not?  If so do you think the number of people who have recovered from Diabetes in the new study is smaller?  Greater?  Why/Why not?  Take a look at each of the confidence intervals - do they overlap?  What does it mean if the confidence intervals overlap (or don't overlap)?

(f) If you had a morbidly obese relative with diabetes what would you tell him or her about bariatric surgery? Explain. Would you recommend it? Why/why not?