PSY 202 Lecture Notes - Lecture 7: Standard Deviation, Formula Vee, Psy
Document Summary
Average deviaion on average, how far from the mean are the scores. Subtract each score from the mean, take absolute value, add them all up, divide by n. Uses the absolute values of the deviaions in order to prevent them from cancelling out. Instead of using absolute values, squares the deviaion before adding them all together in order to avoid cancelling out. Any rounding errors from the mean are simply carried over and then squared --- made larger. In order to avoid these errors, we use the computaional formula. First take sum of squared raw scores (a) Then take sum of all raw scores and square it, divide by n (b) (a-b)/n. Subtract mean from each raw score and square, then sum. If the mean is already speciied, some of the scores will be restricted in order to achieve the sum we need. Degrees of freedom: the number of scores that are free to be whatever they want .
