Mathematics
Categorical Data Analysis Using the Chi-Squared Test
Quick fact
The chi-squared test was developed by Karl Pearson in 1900, and it is one of the most widely used statistical tests in research, appearing in fields from genetics to marketing.
Why this is interesting
If you flip a coin 100 times and get 60 heads, is the coin fair? Or imagine a survey shows men and women have different pet preferences—is that difference real or just by chance?