PSY 295 Lecture Notes - Lecture 2: Standard Deviation, Statistical Parameter
Document Summary
Sum of squared deviations (aka ss or sum of squares) These equations are for a population: change n to n if you are dealing with a sample. Variance is the average squared distance from the mean. Is lower case greek letter sigma (greek for population parameters) Provides a measure of the standard, or average, distance from the mean. = sqrt( 2) = sqrt(ss/n) (these are all for a population, instead we usually use a sample to estimate the population parameter, but with a different equation. ) Formula: variance and standard deviation for a sample. The same as the population formulae with two important differences. Notation: lower case n and english letters instead of greek letters. We divide by n-1 instead of by n. Sample standard deviation: s = sqrt(s2) = sqrt(ss/n-1) Adding or subtracting a constant to/from each score does not change the standard deviation.
