Chi Square Pearson Test. It is the most widely used of many chi squared tests e g yates likelihood ratio portmanteau test in time series etc statistical procedures whose results are evaluated by reference to the chi squared distribution. It is used when categorical data from a sampling are being compared to expected or true results.
This test is used when we have categorical data for two independent variables and we want to see if there is any relationship between the variables. A chi square test is designed to analyze categorical data. For example to see if the distribution of males and females differs between control and treated groups of an experiment requires a pearson s chi square test.
Pearson s chi squared test is used to determine whether there is a statistically significant difference between the expected frequencies and the observed frequencies in one or more categories of a contingency table.
The expected values are calculated based on the known theoretical expectation. That means that the data has been counted and divided into categories. The pearson chi square statistic χ 2 involves the squared difference between the observed and the expected frequencies. Let s take another example to understand this.