For the grouped data 0–10: 5, 10–20: 15, 20–30: 20, 30–40: 8, 40–50: 2 (class interval: frequency), find the median.

n = 50 so n/2 = 25. Cumulative frequencies are 5, 20, 40, 48, 50, so the median class is 20–30 with l = 20, cf = 20, f = 20, h = 10. Median = 20 + ((25 − 20)/20) × 10 = 20 + 2.5 = 22.5. (The middle of the median class, 25, is not the median.)