Question

Mean of 50 observations was found to be 80.4 but later it was discovered that 96 misread as 69 find the new mean

Answer 1

Given

No of observations=50

Mean=80.4

Sum of observations= no of observations xmean

=50x80.4

=4020

Misreaded term =96 and 69

So difference =96-69

=27

Now correct sum of observations =4020+27

=4047

Then mean=4047/50

=80.94


Short cut

Difference=96-69=27

Increase per observation =27/50=0.54

Correct mean=80.4+0.54

=80.94

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