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CA Foundation · Quantitative Aptitude · Statistical Description of Data

A statistician in Chennai has 64 observations and wants to decide the number of classes using Sturges' rule, k = 1 + 3.322 log₁₀ N. Given log₁₀ 64 = 1.806, the suitable number of classes is:

The suitable number of classes is 7. Under Sturges' rule, k = 1 + 3.322 × log₁₀ 64 = 1 + 3.322 × 1.806, which is about 1 + 6 = 7. Forgetting the added 1 would wrongly give 6 classes.

  1. A6
  2. B7Correct
  3. C8
  4. D9

Explanation

3.322 × 1.806 ≈ 6.0, so k = 1 + 6.0 = 7. The choice of 6 comes from forgetting to add the 1 in the formula. The values 8 and 9 would need a much larger N.

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