Why call it Pearson’s chi-squared test?

The term "Pearson's chi-squared test" is named after Karl Pearson, a prominent British mathematician and statistician who made significant contributions to the development of statistical methods in the late 19th and early 20th centuries.

Karl Pearson introduced the chi-squared test as a statistical method for testing the independence or association between categorical variables. He formulated the test and its associated chi-square statistic as part of his work on developing statistical techniques for analyzing contingency tables.

The chi-squared test is commonly used to analyze data in the form of a contingency table, which displays the frequencies or counts of observations for different categories of two or more variables. The test allows researchers to assess whether there is a significant association between the variables based on the observed frequencies in the table.

Given his significant contributions to the development and popularization of the chi-squared test, it is named after Karl Pearson to honor his work in the field of statistics. The use of "Pearson's chi-squared test" distinguishes it from other variants or modifications of the chi-squared test that may exist.

It's worth noting that while Karl Pearson played a crucial role in the development of the chi-squared test, the concept of the chi-square distribution itself predates his work. The chi-square distribution was first introduced by the French mathematician Siméon Denis Poisson in the early 19th century. However, Pearson's application and development of the chi-squared test contributed significantly to its widespread use in statistical analysis.