Statistics: Chi-square
Chi-square goodness-of-fit test is used to test the hypothesis that an observed frequency (distribution) fits a given expected frequency distribution.
For example: observed control and experient proportion, 48% and 52%, fits 50% (expected).
Hypothesis testing:
H0: observed agrees with expected frequency (distribution)
H1: observed frequency does not fit with the expected frequency
Determine critical value: given degrees of freedom, alpha
Calculate Chi-square using the following formation:
If the calculated Chi-square is greater than the Cricial value, then the null hypothesis is rejected. The conclusion is that the observed frequency is different from the expected frequency.