# Statistics > Nonparametrics > 1-Sample Sign Test

This utility performs calculations for testing claims about a population median for the case when the type of population distribution cannot be assumed. The null hypothesis H0 of a claim is median = median0, where median0 is the hypothesized median. The alternative hypothesis H1 can be one of the following: median < median0, median > median0, or median ≠ median0.

A sample value above median0 is assigned a positive (+) sign. A sample value below median0 is assigned a negative (-) sign. The test statistic is computed as follows:

- Left-tailed (H1: median < median0): s = the number of positive (+) signs
- Right-tailed (H1: median > median0): s = the number of negative (-) signs
- Two-tailed (H1: median ≠ median0): s = the minimum of the number of (+) signs and the number of (-) signs

The p-value for a one-tailed test (left-tailed or right-tailed) is P(X ≤ s) where X is a random variable representing the number of positive signs. The p-value for a two-tailed test is 2P(X ≤ s).

If the sample size n (excluding values that are equal to the hypothesized mean) is not more than 50, exact binomial probability calculations are used to compute the p-value. If the sample size is greater than 50, the normal distribution is used as an approximation to binomial:

To use the utility, follow these steps:

- If individual samples are entered in a single column of the Datasheet, select the Samples in column: radio button, and select the column name in the drop-down menu.
- To use summary statistics of the sample data, select the Summarized sample data: radio button, and input the number of positive signs and the number of negative signs in the provided text fields.
- Select the form of the alternative hypothesis in the Alternative Hypothesis: drop-down menu. Enter the hypothesized population median in the provided text box.
- Click the OK button to perform the computation. The results will be displayed in the log window.