# Psychology 2810 Lecture 12: lecture 12

## Document Summary

Tables on p. 818 (lower cut off) and 819 (higher cut off) Which tail matters depends on the size of sigma---- big sigma look at right table, small sigma left page (818) Some properties: mean = n-1 = degrees of freedom, distribution changes with n, both the mean and the shape. !1: kai squared is always greater than or equal to zero. Never negative: always a skew to the right, longer tail to the right. Con dence interval: n-1 * s^2 / kai ^2 (upper) and n-1 * s^2 / kai^2 (lower) represent lower and upper bound numbers, respectively (represent the middle xx% of sigma^2 values. The upper cut off will give you the lower bound, and vice versa: the point estimate will always be in the interval, but not in the middle of them--- not a symmetric, closer to lower bound than higher.