Question

What does it mean that mean of error ? Does it also mean that mean of variance is zero? What is the difference between population mean and sample mean?

Answer 1

Mean of error is defined as the average value of the mean calculated by subtracting each value of sample with the mean of the sample.

Mean of Error can be written as

$\frac{\sum X- \bar{X}}{n}$

No, it does not mean that mean of variance is zero, if the variance is Zero than it mean that all the values in the sample has same value and hence there will be no error.

Population mean and sample mean are somewhat similar but if the value taken from a sample and hence the average value of the sample is calculated then it will ne called as Sample mean .It is denoted by X(bar)

And if population is considered in calculating the average values of the element hence it will be called as population mean, it is denoted by 'u'