Multiple choice

What is the mean of the given data? | Class interval | 0 – 30 | 30 – 60 | 60 – 90 | 90 – 120 | 120 – 150 | 150 – 180 | | --- | --- | --- | --- | --- | --- | --- | | Frequency | 8 | 15 | 16 | 20 | 12 | 9 |

  1. 43

  2. 55

  3. 61

  4. 90

  5. 72
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D Correct answer
Explanation

Midpoints: 15, 45, 75, 105, 135, 165. Frequencies: 8, 15, 16, 20, 12, 9. Sum of f*x = 120 + 675 + 1200 + 2100 + 1620 + 1485 = 7200. Total frequency = 80. Mean = 7200 / 80 = 90.

AI explanation

First, find the midpoints of the class intervals: 15, 45, 75, 105, 135, and 165. Multiply each midpoint by its frequency and sum them: (15*8) + (45*15) + (75*16) + (105*20) + (135*12) + (165*9) = 120 + 675 + 1200 + 2100 + 1620 + 1485 = 7200. The total frequency is 8 + 15 + 16 + 20 + 12 + 9 = 80. Dividing 7200 by 80 gives a mean of 90.

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