The sum of deviations of certain numbers of items measured from 4 is 72 and the sum of deviations of the items from 7 is -3. Find the number of items and mean.
Dear Student,
Let "n" be the required number of observations.
Σ(x i - 4) = 72, therefore, Σxi - 4n = 72 ....... (1)
And,
Σ(xi - 7) = -3, therefore, Σxi - 7n = -3 ........ (2)
Subtracting the above two equations we get,
3n = 75
n = 25
Putting n = 25 in Σxi - 4n = 72,
Σxi - 4(25) = 72
Σxi = 72 +100
Σxi = 172
Mean = Σxi
n
= 172/ 25 = 6.88
Regards,
Let "n" be the required number of observations.
Σ(x i - 4) = 72, therefore, Σxi - 4n = 72 ....... (1)
And,
Σ(xi - 7) = -3, therefore, Σxi - 7n = -3 ........ (2)
Subtracting the above two equations we get,
3n = 75
n = 25
Putting n = 25 in Σxi - 4n = 72,
Σxi - 4(25) = 72
Σxi = 72 +100
Σxi = 172
Mean = Σxi
n
= 172/ 25 = 6.88
Regards,