Mean of 25 observations was found to be 78.4. But later it has been discovered that 96 was misread as 69. Find correct mean
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Answered by
17
mean of 25 = 78.4
incorrect Sum = 78.4×25= 1960
correct sum = 1960+96-69
= 1987
correct mean = 1987÷25= 79.48
incorrect Sum = 78.4×25= 1960
correct sum = 1960+96-69
= 1987
correct mean = 1987÷25= 79.48
Answered by
19
Mean = sum of observations / total no:of observations
sum of observations = Mean × total no:of observations
= 78.4 × 25
= 1960
As 96 is the correct observation and 69 is the incorrect , we have to add 96 to sum of observations and subtract 69 from it.
New sum = 1960 + 96 - 69
= 1987
Mean = sum of observations / total no:of observations
= 1987 / 25
= 79.48
sum of observations = Mean × total no:of observations
= 78.4 × 25
= 1960
As 96 is the correct observation and 69 is the incorrect , we have to add 96 to sum of observations and subtract 69 from it.
New sum = 1960 + 96 - 69
= 1987
Mean = sum of observations / total no:of observations
= 1987 / 25
= 79.48
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