Essentials of Statistics for the B...

8th Edition
Frederick J Gravetter + 1 other
ISBN: 9781133956570



Essentials of Statistics for the B...

8th Edition
Frederick J Gravetter + 1 other
ISBN: 9781133956570
Textbook Problem

In the previous problem we noted that the differences in cognitive skills tend to be bigger among older people than among younger people. These differences are often called diversity. Similarly, the differences in performance from trial to trial for the same person are often called consistency. Research in this area suggests that consistency of performance seems to decline as people age. A study by Wegesin and Stem (2004) found lower consistency (more variability) in the memory performance scores for older women than for younger women. The following data represent memory scores obtained for two women, one older and one younger, over a series of memory trials.

a. Calculate the variance of the scores for each woman.

b. Are the scores for the younger woman more consistent (less variable)?

Younger Older
8 7
6 5
6 8
7 5
8 7
7 6
8 8
8 5


To determine

To Find: The variance scores for each group.


Given info:

The information shows the memory scores of the younger women and older women.


The formula for calculating the mean is,


The formula for calculating the variance is,


For younger women:

The mean for younger women is,


The variance for younger women is,



To determine

To find: The reason that the younger woman is more consistent than the older woman.

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