Chi-squared test

Chi-squared test (or formula_1 test) is a statistical hypothesis test. It usually tests the hypothesis that "the experimental data does not differ from untreated data". That is a null hypothesis. The distribution of the test statistic is a chi-squared distribution when the null hypothesis is true.
The test results are regarded as 'significant' if there is only one chance in 20 that the result could be got by chance.
Groups.
There are three main groups of tests: