Question

The mean of 50 observations of a data was 70. At later stage it is noticed that a value 85was wrongly read as 60. Find the value of correct mean.

Answer 1

Old mean= sum of 50 observations/50
70*50= sum of observations
3500= sum
Now, 85 was wrongly read 60 therefore, we will need to add 15(85-60) to the sum of observations to get correct mean 
Therefore, correct mean= (3500+15)/50
= 3515/50
=70.3 
Therefore, 70.3 is correct mean

Answer 2

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Old mean= sum of 50 observations/50

70*50= sum of observations

3500= sum

Now, 85 was wrongly read 60 therefore, we will need to add 15(85-60) to the sum of observations to get correct mean

Therefore, correct mean= (3500+15)/50

= 3515/50

=70.3

Therefore, 70.3 is correct mean.

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