Chi² Test (goodness of fit)

X² test is a test of distributions

Think of it as a way to compare histograms

You will compare one set of data to "what you expected to get"
 
 

Test statistic = X² = Sum of (observed – expected)²
                                                        expected

Look up the critical value

df = degrees of freedom = number of categories – 1

Reject null hypothesis if X² > critical value of X²