bchadwick

// this is incorrect Variance = [(12.5)^2+(22.5)^2+(32.5)^2+(42.5)^2]/(41)
Variance = [(12.5)^2+(22.5)^2+(32.5)^2+(42.5)^2]/4 because the population is known mean is known.
Therefore, variance = 5/4 as Swissaholic pointed out.