Given:

A nutrition store in the mall is selling "Memory Booster" which is a concoction of herbs and minerals that is intended to improve memory performance. To test the hypothesized memory enhancement of the herbal mix, the now famous drug researcher, Dr. Mindfog, obtains a sample of 15 adult volunteers and has each person take the suggested dosage each day for 4 weeks. At the end of the four-week period, each individual takes a standardized memory test. In the general adult population, the standardized memory test is known to have a mean of= 10, where higher scores demonstrate better performance on the test of memory. The scores for the 15 volunteers are:

12, 11, 13, 15, 8, 11, 13, 15, 10, 9, 10, 16, 15, 11, 14

With= .01, determine the critical value of z* , t*, or r* that needs to be employed here. The value is:

Group of answer choices

.641

2.58

2.624

2.947

2.977

the correct value of z* , t*, or r* is not listed in alternatives "a" through "e"