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t Test for Paired Samples Help

The paired sample comparison t test is used when the samples are not independent. For example, you might want to compare two analytical test methods. You take a series of samples; mix them well; divide them in half; and run one-half in one analytical test method and the other half in the second analytical test. The samples are not independent in this case. You can use this test to determine if there is a significant difference in the two tests. You 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 differences in paired samples. The example below demonstrates how to perform the paired samples comparison.

A medical researcher wants to compare two methods of measuring cardiac output. Method A is the standard method and is considered very accurate. But this method is invasive. Method B is less accurate but not invasive. Cardiac output from 26 patients was measured using both methods. We want to sue the paired sample t test to determine if there is a significant difference between the two methods.

t Test for Paired Samples Comparison Output

The output from the example data (using a hypothesized difference = 0) is shown below. 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.

A plot of the confidence interval is also given:

There is also a chart of the difference 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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