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10 is the mean of a set of 7 observation...

10 is the mean of a set of 7 observations and 5 is the mean of a set of 3 observations, the mean of the combined set is

A

15

B

10

C

8.5

D

none of these

Text Solution

Verified by Experts

The correct Answer is:
C
We have,
`n_(1)=7, bar(X_(1))=10, n_(2)=3 and bar(X_(2))=5`
Let `bar(X)` be the Mean of the combined set. Then,
` bar(X)=(n_(1)bar(X_(1))+n_(2)bar(X_(2)))/(n_(1)+n_(2))=(7xx10+3xx5)/(7+3)=8.5`
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