Data Analysis with Microsoft Excel: Updated for Office 2007

262 Fundamentals of Statistics

According to the output, the average revenue for nonrural homes is

$16,821, whereas for rural homes it is $12,827. The data suggest that

nonrural homes generate more revenue, but the p value for the t test is 0.057,

which would cause us not to reject the null hypothesis. The 95% confi dence

interval for the difference in revenue ranges from 2 $118 to $8,106.

However, the tests for equality of variance are all nonsignificant. The

F test p value equals 0.698, the p value of Bartlett’s test equals 0.732, and

the p value for Levene’s test equals 0.444. This would lead us to believe that

we can use a pooled estimate for the population standard deviation. Let’s

redo the test, this time with that assumption.

To change the output to display the results of a pooled test:

1 Click cell D5 in the t Test worksheet.

Cell D5 contains the value TRUE if a pooled test is used and FALSE

for unpooled test.

2 Replace FALSE with TRUE in cell D5.

The output changes to display the pooled test results. See Figure 6-21.

Figure 6-20
Results of the
two-sample
t test analysis
with unpooled
variance

difference in the

sample averages

t statistic degrees of freedom 95% confidence interval for

the difference in sample

means

conditions of the hypothesis test

assumes unpooled variance descriptive statistics

pvalue