A chi-square model is a statistical method used to analyze the results of certain types of experiments. It involves a comparison of the deviation of real observations from expected values, and helps determine whether a result is significant or not. It has been a particularly useful model in the development of new drugs.

The chi-square function was first proposed in 1900 by a British statistician, Karl Pearson. He developed a formula which takes in consideration the squares of the deviations of each observation from the expected value and weighs them accordingly. By using this distribution, he was able to show whether or not the results from a certain data set matched the expected results from the total population. In this way he developed a measure of the"goodness of fit" for a data set. He also developed a method for comparing the relationship between two data parameters...