Posted by **Komal** on Tuesday, October 23, 2012 at 4:46pm.

A researcher hypothesizes that a new herbal supplement improves memory. A sample of n = 25 college students is obtained and each student takes the supplement daily for six weeks. At the end of the 6-week period, each student is given a standardized memory test, and the average score for the sample is M = 55. For the general population of college students, the distribution of test scores is normal with a mean of µ = 35 and a standard deviation of σ =10. Assume you're using a one-tailed test with alpha = .01.

1. What z-score marks the boundary for the critical region? Round your answer to the nearest tenth. Do not write anything else in the answer blank.

2. Do you reject or fail to reject the null hypothesis? Write either Reject or Fail to Reject. Write only one answer or the other, do not write anything else in the answer blank, and do not include periods or other punctuation.

- stats -
**MathGuru**, Tuesday, October 23, 2012 at 6:09pm
1. FOR A ONE-TAILED TEST with alpha .01 = 2.33 (round accordingly)

2. Use a z-test to determine your test statistic.

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

Your data:

sample mean = 55

population mean = 35

standard deviation = 10

sample size = 25

Substitute the values above into the z-test and calculate. If the test statistic exceeds the critical value, then reject the null. If the test statistic does not exceed the critical value, fail to reject the null.

I hope this will help get you started.

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