Multiple choice

The combined mean of the following data is Group A B C Number of observations 400 250 350 Mean 52 44 60

  1. $52.8$
  2. $44$
  3. $52$

  4. None of them
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A Correct answer
Explanation

The combined mean is calculated as (Sum of all observations) / (Total number of observations). Sum = (400*52) + (250*44) + (350*60) = 20800 + 11000 + 21000 = 52800. Total observations = 400 + 250 + 350 = 1000. Mean = 52800 / 1000 = 52.8.

AI explanation

The combined mean formula is the sum of each group size times its mean divided by the total observations. This calculates to (400 times 52 plus 250 times 44 plus 350 times 60) divided by 1000, yielding 52800 divided by 1000, which equals 52.8.

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