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CMA Foundation · Fundamentals of Business Mathematics and Statistics · Statistical Representation of Data

In a frequency distribution with equal width classes, the mid-value of the first class is 25 and the mid-value of the fifth class is 65. If the lowest class begins at its lower limit, what is the lower limit of the first class?

The lower limit of the first class is 20. The mid-values differ by 40 across four steps, giving a class width of 10, and subtracting half the width, 5, from the first mid-value 25 gives 20.

  1. A15Correct
  2. B20
  3. C10
  4. D25

Explanation

Four class widths separate the mid-values: (65 - 25) / 4 = 10, so width is 10. Lower limit = mid-value - width/2 = 25 - 5 = 20. Check: classes 20-30 (mid 25) up to 60-70 (mid 65) fits. So the answer is 20, not 15, which wrongly subtracts a full width/2 twice.

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