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# z and t Tests for Difference in Two Means Help

This test compares the means of two samples. The test will provide a confidence interval for the difference in two means and has the option for hypothesis testing as well. The test accounts automatically for variances that are equal or unequal.

You have the following two options:

You also have the option for a two-sided, lower one-sided or an upper one-sided test.

The data can be in a range in a worksheet or the user can enter an average, standard deviation, and sample size for the two processes. The example below demonstrates how to do this test using data in a range in the worksheet.

A company uses two different processes to put sand into bags. The question is whether each process places the same weight into the bags. Ten bags from each process were weighed. The data are shown below. We want to see if there is a difference in the means from the two processes.

#### Difference in Two Means Output

The output from the example data (using the t test) is shown below. The hypothesized difference in means 0 in this example. An explanation of terms is given below the output.

The output tells you the conclusion from the test. The null hypothesis (H0) and the alternate hypothesis (H1) are printed below the title.

Notes:

A plot of the confidence interval is also given. This makes it easy to see the relationship between the hypothesized difference and the confidence interval.

There are also charts for both process data to look for possible outliers. If the program detects possible outliers, they will be in red and a message will be printed on the worksheet.

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