Quartiles divide a sorted dataset into four equal parts.
Q1 = 25th percentile. Q2 = median. Q3 = 75th percentile.
IQR = Q3 − Q1. Data below Q1 − 1.5×IQR or above Q3 + 1.5×IQR are outliers.
IQR (Interquartile Range) = Q3 − Q1. It covers the middle 50% of your data.