CMA Foundation · Fundamentals of Business Mathematics and Statistics · Statistical Representation of Data
A frequency distribution has the inclusive classes 10-19, 20-29, 30-39 and 40-49. What are the true (exact) class limits of the class 30-39 after converting to an exclusive form?
The true class limits are 29.5 to 39.5. The gap between consecutive inclusive classes is 1, so half of it, 0.5, is subtracted from the lower limit 30 and added to the upper limit 39 to make the classes continuous.
- A30 to 39
- B29.5 to 39.5Correct
- C30.5 to 39.5
- D29 to 40
Explanation
The gap between the upper limit of one class (29) and the lower limit of the next (30) is 1. Half of this gap is 0.5, which is subtracted from each lower limit and added to each upper limit. So 30-39 becomes 29.5-39.5. Option 30.5 to 39.5 applies the correction only to the upper limit, so it is wrong.
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