The chi-square statistic is used to compare two categorical variables to see if they are related

The chi-square statistic is used to compare two categorical variables to see if they are related.

Calculating the statistic involves looking the figure up in the chi-square table. we shall need to know degrees of freedom and probability (both of which are usually supplied in the question).

Step 1: Calculate the number of degrees of freedom. This number may be given to you in the question. If not then the degrees of freedom equals the number of classes (categories) minus one. i.e. ##d.f.=k-1##

Step 2: Find the probability that the phenomenon we are investigating would occur by chance. This is usually stated in the question. In the sample question, we are given the probability of 5%, or 0.05.

Step 3: Look up degrees of freedom and probability in the chi-square table. One degree of freedom and 5 percent probability equals 3.84 in the chi-square table. This is your critical chi-square value.