Statisticshard · Past Paper
If the arithmetic mean of 10 items is 20 and the mean of 20 items is 10, what is the combined mean of all 30 items?
A13.33
B15
C16.66
D20
✓ Correct Answer: A — 13.33
Combined Mean = (n1*m1 + n2*m2) / (n1+n2) = (10*20 + 20*10) / (10+20) = 400 / 30 = 13.33.
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