Posted by **Richard** on Wednesday, April 4, 2012 at 5:22pm.

The Deborah Heart Institute performs many open-heart surgery procedures. Recently research physicians at the Institute developed a new heart bypass procedure that they believe reduces the average length of recovery. The hospital board will not adopt the procedure unless there is substantial evidence to suggest that it is better than the current procedure. Records indicate that the mean recovery rate for the current procedure is 42 days with a standard deviation of 5 days. Test this hypothesis on a sample=36 patients and a sample mean of 40.2 days using a rejection region.

- Statistics -
**MathGuru**, Wednesday, April 4, 2012 at 7:30pm
Try a one-sample z-test.

Hypotheses:

Ho: µ = 42 -->null hypothesis

Ha: µ < 42 -->alternate hypothesis

z = (sample mean - population mean)/(standard deviation divided by the square root of the sample size)

With your data:

z = (40.2 - 42)/(5/√36) = ?

Finish the calculation.

Check a z-table at the level you wish to use for the rejection region.

If the z-test statistic exceeds that value from the z-table, reject the null and conclude µ < 42. If the z-test statistic does not exceed the that value from the z-table, do not reject the null (you cannot conclude a difference).

I hope this will help get you started.

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