Multiple choice

A set of $7$ observations has mean $10$ and another set of $3$ observations has mean $5 .$ The mean of combined set is:

  1. $15$
  2. $10$
  3. $8.5$
  4. $7.5$
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C Correct answer
Explanation

Combined mean = (Sum of observations) / (Total count). Sum = (7 * 10) + (3 * 5) = 70 + 15 = 85. Total count = 7 + 3 = 10. Mean = 85 / 10 = 8.5.

AI explanation

The sum of the first set of observations is 7 * 10 = 70, and the sum of the second set is 3 * 5 = 15. The combined mean is the total sum divided by the total number of observations: (70 + 15) / 10. The result is 85 / 10, which equals 8.5.

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