Calculate the mean of the following Class interval Frequency 90 - 100 10 80 -…
2024
Calculate the mean of the following
Class interval Frequency
90 - 100 10
80 - 90 15
70 - 80 14
60 - 70 12
50 - 60 9
- A.
73.2
- B.
75.8
- C.
74.6
- D.
71.5
Attempted by 21 students.
Show answer & explanation
Correct answer: B
Solution:
Find the midpoint (xi) for each class interval by averaging the class limits: 90–100 → 95, 80–90 → 85, 70–80 → 75, 60–70 → 65, 50–60 → 55.
Multiply each midpoint by its frequency (fi·xi): 10·95 = 950, 15·85 = 1275, 14·75 = 1050, 12·65 = 780, 9·55 = 495.
Sum the frequencies and the products: Σfi = 10 + 15 + 14 + 12 + 9 = 60. Σ(fi·xi) = 950 + 1275 + 1050 + 780 + 495 = 4550.
Compute the mean: Mean x̄ = Σ(fi·xi) ÷ Σfi = 4550 ÷ 60 = 75.8333… ≈ 75.8 (rounded to one decimal place).