Pearson Chi Square Test Formula. To reduce the error in approximation frank yates suggested a correction for continuity that adjusts the formula for pearson s chi squared test by subtracting 0 5 from the absolute difference between each observed value and its expected value in a 2 2 contingency table. Formula chi 2 sum limits i n frac o i e i 2 e i.
This is the percent probability divided by 100 that a specific chi square value was obtained by chance alone. The following are the important properties of the chi square test. Algebraically speaking x 2.
For example we have different treatments treated and nontreated and treatment outcomes cured and noncured here we could use the chi square test for independence to check whether treatments are related to treatment outcomes.
Df k 1 where k equals the number of groups. If you are comparing tabular data the degrees of freedom equals the number of rows minus 1 multiplied by the number of columns minus 1. Formula chi 2 sum limits i n frac o i e i 2 e i. Algebraically speaking x 2.
