What formula do I use to solve: A sample with a mean of M = 40 and a variance of s2 = 20 has an estimated standard error of 2 points. How many scores are in the sample?

Answer 1

standard error = s/√n

Note: The square root of the variance is called the Standard Deviation

With your data:
2 = (4.472)/√n

Solve for n.

I hope this is what you were asking.