What Is Chi-Square Test?
A chi-square test compares observed category counts against the counts you'd expect under some assumption, then measures how far apart they are. A small chi-square value means the data roughly matches expectations; a large one suggests something is genuinely different from the assumption. It's a common tool for goodness-of-fit tests, like checking whether a die is fair.
Example
Rolling a fair six-sided die 60 times, you'd expect 10 rolls of each number. If the actual counts were far from 10 each, the chi-square value would be large, suggesting the die isn't fair.