Math CentralQuandaries & Queries


Question from Abhishek, a student:

Mean of 50 observations was found to be 80.4 but later all it was discovered 96 was mistake at 69
Find the correct mean?

Hi Abhishek,

Suppose that the sum of the 50 observations is $S,$ then you know that

\[\frac{S}{50} = 80.4\]


\[S = 50 \times 80.4 = 4020.\]

How much does that sum $S$ change after fixing the error? What is the new mean?


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