Multiple choice

5 students of a class have an average height 150 cm and variance 18 cm2. A new student, whose height is 156 cm, joined them. The variance (in cm2) of the height of these six students is:

  1. 22

  2. 20

  3. 16

  4. 18
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Original sum of squares = 5 * (18 + 150^2) = 405090. New sum of squares = 405090 + 156^2 = 429426. New mean = (5 * 150 + 156) / 6 = 151. New variance = (429426 / 6) - 151^2 = 71571 - 22801 = 20.

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