# 17.3.6 Two Sample Test for Variances (Pro Only)

## Introduction

This function performs F-test for testing whether the variance from one population equals, greater or less than the other one, and then creates a confidence interval for the sample variance ratio.

The F-test statistic is a generalization of the t-test statistic, and is a scalar random variable. The F-test statistic can be calculated as a ratio of the variances of two samples, and so can be used to test whether or not data samples come from populations with equal variances.

The F-Test statistic and p-value will be calculated so that you can decide whether or not to reject the null hypothesis. A small P-value, which less than a significance level $\alpha\,\!$ , indicates that you can reject the null hypothesis

## Handling Missing Values

The missing values in the data range will be excluded in the analysis

From Origin 2015, missing values in the grouping range and the corresponding data values will be excluded in analysis. In the previous version, missing values in the grouping range will be considered as a group.

## Performing Two Sample Test for Variances

To perform a two-sample test for variances:

1. Select Statistics: Hypothesis Testing: Two-Sample Test for Variances. This opens the TwoSampleTestVar dialog box.
2. Specify the Input Data Form (Indexed or Raw) and then fill Input Data, the F-test for Variances Ratio, and the Alternate Hypothesis.
3. Upon clicking OK, an analysis report sheet is generated that lists degrees of freedom, F-statistics, the associated p-value, and the test conclusion. In addition, you can produce the confidence intervals for the sample variances ratio, histogram and box chart, and the power analysis.
 Topics covered in this section: Tutorial