Team # 4 Chi-Square, Goodness-of-Fit Test In scientific research, the validity of experimental results is established by performing particular statistical tests. Chi-square, Goodness-of-Fit, is a test that determines the degree to which two sets of data are similar. This is what "goodness-of-fit" refers to. The Chi-square statistic (x2) does this by calculating the amount of deviation between the two data sets. It is commonly used to compare observed versus expected results, making it the perfect analysis in genetics research. Observed values are the data you collect to test a hypothesis. Expected values must be calculated based on a hypothesis. They are a prediction and can be determined by using probabilities: EXPECTED value = (probability) X (sample size). Here are 2 things to remember about probability (symbolized as "P" below): P(event) = # favorable outcomes and 0s P(event) $ 1