Question

The following table gives the life time of 200 bulbs. Calculate the mean life time of a bulb by step deviation method :
Life time in hrs No. of bulbs
400 - 499 24
500 - 599 47
600 - 699 39
700 - 799 42
800 - 899 34
900 - 999 14

Answer 1

Thank you for asking this question. Here is your answer:

We will assume the mean to be A = 549.5

Mean, x = a + ( ∑fiui/ ∑fi x h)

= 649.5 + 57/200 x 100

= 649. 5 + 28.5

= 678

So the mean life span of the bulb is 678

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Answer 2

here's your answer...
hope it helped...