Data Analysis with Microsoft Excel: Updated for Office 2007

Chapter 6 Statistical Inference 245

There are two observations from each city, and the observations consti-

tute paired data. You’ve been asked to determine whether this sample of

19 cities demonstrates a statistically signifi cant increase in the percentage

of women in the workforce. Let m be the mean change in the percentage of

women in the workforce. You have two hypotheses.

H 0 : m 5 0 (There is no change in the percentage from 1968 to 1972.)

Ha: m Z 0 (There is some change, but we’re not assuming the direction

of the change.)

You can use StatPlus to test these hypotheses and create a t confi dence

interval for the change in percent from 1968 to 1972. Do this now by analyz-

ing the Diff variable to test whether the average difference is signifi cantly

different from zero.

To test whether there is a signifi cant difference:

1 Click One Sample Tests from the StatPlus menu and then click

1 Sample t test.

We use the one-sample t test because we are essentially looking at

one sample of data—the sample of paired differences.

Figure 6-11
The Labor
workbook