Pearson correlation is used when both variables are continuous and normally distributed. It shows the strength and direction of a linear relationship. For example, we can use it to see if higher study time is related to higher test scores. This test needs data measured at the interval or ratio level and assumes normality.

Spearman’s rho is a good choice when the data is not normal or when variables are ordinal. It checks if there is a consistent order in the relationship. For example, it can show if students with higher class rankings also have better behavior ratings.

The Chi-square test is used for categorical variables. It shows if there is a relationship between two categories, like gender and favorite subject. It does not require normality.

Choosing the correct test is important. We must look at data type and normality to avoid wrong results.