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CA Foundation · Quantitative Aptitude · Statistical Description of Data

A frequency polygon is to be drawn for the following distribution of marks: 0–10: 4, 10–20: 9, 20–30: 15, 30–40: 7. Which set of points (x, y) correctly gives the vertices of the polygon, excluding the two end points on the x-axis?

The vertices are (5,4), (15,9), (25,15) and (35,7). A frequency polygon plots each class mark (midpoint) against its class frequency. Using class limits or cumulative frequencies would be incorrect for a polygon.

  1. A(10, 4), (20, 9), (30, 15), (40, 7)
  2. B(5, 4), (15, 9), (25, 15), (35, 7)Correct
  3. C(0, 4), (10, 9), (20, 15), (30, 7)
  4. D(5, 4), (15, 13), (25, 28), (35, 35)

Explanation

A frequency polygon plots class marks against frequencies. Class marks are 5, 15, 25, 35, so the points are (5,4), (15,9), (25,15), (35,7). Options with upper or lower limits on the x-axis are wrong, and the last option uses cumulative frequencies, which belong to an ogive.

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