Critical Chi-squared value

The critical chi-squared value is the value that we compare our calculated chi-squared value to, to determine whether our data is significantly different from the expected values.

We can find it in a big table, called the chi-squared distribution table, which gives us the critical value based on two variables:

• The significance level
• The degrees of freedom of our contingency table

You need to use the column heading that corresponds to one minus your chosen significance level. For example, if you chose a significance level of 5% (0.05), you would look under the column heading for 0.95 (1 - 0.05 = 0.95).

We should now have two things:

• Our calculated chi squared value
• The critical chi-squared value from the table

If our calculated chi-squared value is greater than the critical chi-squared value, then we can say that there is significant evidence to suggest that the two variables are not independent.