This dialog is activated by selecting the **Mood's Median Test...** command from the Statistics -> Nonparametric Tests -> menu. It can be used in order to test whether several samples originate from the same distribution.

QtiPlot combines the scores from the k input samples in the *Selected Data* box.
These N values (*N = n1 + n2 +...+ nk*, where *nj* are the individual sizes of each sample) are sorted and an overall median is calculated. Afterwards QtiPlot creates a frequency table and displays the number of scores in each sample below (*N1j*) and above (*N2j*) the previousely calculated median, where *R1 = N11 + N12 +...+ N1k*, *R2 = N21 + N22 +...+ N2k* and *j = 1, 2,...,k*.

The test statistic (*Chi2*) is calculated using the following formula:

where *Eij = Ri*nj/N*, *j = 1, 2,...,k* and *i* can be either 1 or 2.

QtiPlot computes an approximated p-value, which is the probability of a chi-squared value of at least *Chi2* being observed: *1 - chi2cdf(Chi2, k - 1)*. The null hypothesis is rejected if the approximated probability is lower than the value of the significance level.

The data sets selected in the *Available data* window can be added to the analysis either by pressing the left to right arrow button or by dragging and dropping them onto the right side window.