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CA Foundation · Quantitative Aptitude · Statistical Description of Data

A frequency table uses inclusive class intervals 10–19, 20–29, 30–39 and so on. What are the true class boundaries of the class 20–29?

The true class boundaries are 19.5 and 29.5. In an inclusive series the gap between 19 and 20 is 1, so half of it, 0.5, is deducted from the lower limit and added to the upper limit, making the class continuous with its neighbours.

  1. A20 and 30
  2. B19.5 and 29.5Correct
  3. C20.5 and 29.5
  4. D19 and 30

Explanation

The gap between the upper limit of one class (19) and the lower limit of the next (20) is 1. Half of it, 0.5, is subtracted from every lower limit and added to every upper limit. So 20–29 becomes 19.5–29.5. Option A just reads off the limits and leaves the gap unadjusted.

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