The Chi Square distribution is a mathematical distribution that is used directly or indirectly in many tests of significance. The most common use of the chi square distribution is to test differences among proportions. although this test is by no means the only test based on the chi square distribution, it has come to be known as the chi square test. The chi square distribution has one parameter, its degrees of freedom (df). It has a positive skew; the skew is less with more degrees of freedom. As the df increase, the chi square distribution approaches a normal distribution. The mean of a chi square distribution is its df. The mode is df - 2 and the median is approximately df - 0 .7.