Multiple choice

Calculate mean age from the following data: Age (in years) 21 – 25 16 – 20 11 – 15 26 – 30 Frequency 4 2 8 6

  1. 20

  2. 30

  3. 40

  4. 50
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A Correct answer
Explanation

Using midpoints: 23 (freq 4), 18 (freq 2), 13 (freq 8), 28 (freq 6). Mean = (23*4 + 18*2 + 13*8 + 28*6) / (4+2+8+6) = (92 + 36 + 104 + 168) / 20 = 400 / 20 = 20.

AI explanation

Rearranging the classes gives intervals from 11 to 15, 16 to 20, 21 to 25, and 26 to 30, with corresponding midpoints of 13, 18, 23, and 28. The sum of the midpoints multiplied by their frequencies is (13 times 8) + (18 times 2) + (23 times 4) + (28 times 6), resulting in 400. Dividing this by the total frequency of 20 gives a mean age of 20.

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