Multiple choice

The mean of 12 observations is 20 if every observation is decreased by 2 find the new mean

  1. $18$
  2. $16$
  3. $12$
  4. $-10$
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A Correct answer
Explanation

If every observation in a set is decreased by a constant k, the mean of the set also decreases by k. Here, 20 - 2 = 18.

AI explanation

The total sum of the 12 observations is 12 times 20, which is 240. When every observation is decreased by 2, the total sum decreases by 12 times 2, or 24, making the new sum 216. Dividing this new sum by 12 gives a new mean of 18.

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