Essential Statistics

592

Chapter 13: Confidence Intervals – Small Samples

Note:

In the above example, the data was available so you would have to

use the portion of the workbook which allows you to enter data to compute

the confidence interval.

Section Review

13-4 Small Sample Confidence Interval for the Difference

Between Two Population Means Using Independent

Samples

Here we will present theory that will enable us to determine, based on some

specified conditions

, whether the true value of the difference between two

population means will lie within an interval of values with a specified

confidence.

Specified Conditions

: Samples of size

< 30 will be obtained from two

normal populations with unknown standard deviations.

First, we will consider estimating the difference between two population

means based on those specified conditions.

Figure 13-8

shows the design of

the situation at hand. We will be sampling from two normal populations

with an unknown respective means

and

and standard deviations

and

for a particular quantitative variable. Samples of size

and

will be

obtained from the two respective populations and the sample means

and

, and the sample standard deviations

and

will be computed.