Multiple choice

If 10 and 15 are the means of 5 and 10 observations, respectively, what will be the mean of all 15 observations?

  1. 1.67

  2. 6.67

  3. 2.67

  4. 13.3
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D Correct answer
Explanation

The total sum of observations is (5 * 10) + (10 * 15) = 50 + 150 = 200. The mean of all 15 observations is 200 / 15 = 13.33.

AI explanation

The combined mean formula is the total sum of all observations divided by the total number of observations. The sum of the first set is 5 multiplied by 10, giving 50; the sum of the second set is 10 multiplied by 15, giving 150. The combined sum is 50 plus 150, which equals 200. Dividing this total sum by the total number of observations, which is 15, gives 200 divided by 15, which equals 13.3.

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