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The mean life of a sample of 60 bulbs wa...

The mean life of a sample of 60 bulbs was 650 and the standard deviation was 8 h. A second sample of 80 bulbs has a mean life of 660 h and standard deviation 7h. Find the over all standard deviation.

A

`8.97`

B

`8.98`

C

`8.94`

D

None of these

Text Solution

Verified by Experts

The correct Answer is:
C
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