CA Foundation · Quantitative Aptitude · Statistical Description of Data
In a frequency distribution with equal class widths, the class marks of the first three classes are 15, 25 and 35. What are the class limits of the first class, if the classes are exclusive?
The first class is 10-20. Consecutive class marks differ by 10, so the class width is 10. Half of this width, 5, is subtracted from and added to the class mark 15, giving lower limit 10 and upper limit 20.
- A10-20Correct
- B15-25
- C5-25
- D10-15
Explanation
The class width = 25 - 15 = 10. The first class has mid-value 15, so its limits are 15 - 5 = 10 and 15 + 5 = 20, giving 10-20. The option 15-25 treats the mark as the lower limit, which is wrong.
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