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CMA Foundation · Fundamentals of Business Mathematics and Statistics · Statistical Representation of Data

The marks of 60 trainees are grouped as 0-10: 5, 10-20: 12, 20-30: 20, 30-40: 15, 40-50: 8. A frequency polygon is closed at both ends by adding two imaginary classes with zero frequency. What is the total number of points joined to form the closed polygon, and what is the mid-point of the added class on the right?

The closed polygon has 7 points, with mid-point 55 for the added right-hand class. Five actual classes are joined with two imaginary zero-frequency classes, one before 0-10 and one after 40-50, which is 50-60 with mid-point 55.

  1. A5 points; mid-point 55
  2. B7 points; mid-point 45
  3. C7 points; mid-point 55Correct
  4. D6 points; mid-point 55

Explanation

There are 5 actual classes plus 2 imaginary classes (-10-0 and 50-60), giving 7 points. The right added class is 50-60, with mid-point 55. Option 45 is the mid-point of the last actual class.

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