Stat 322 – Day 14 ANOVA and Multiple Comparisons

Announcements No Tuesday 12-1 office hour this week HW 4 posted online, due Friday Writing Assignment 4 posted with HW 4, due Monday Tuesday talk, Science North Room 201  Cost-Sensitive Boosting: An Estimation Procedure when the Average is not the ‘Gold Standard’  Brian Kriegler, UCLA  Writing Assignment….

Previously When want to compare several population means (or treatment means), can use Analysis of Variance  H 0 :  1 = … =  I  H a : not all  i equal  Compare variability in sample means, MSTr, to (pooled) variability within groups, MSE  F = MSTr/MSE with df I-1 and N-I Is it large?

Handicap Discrimination Minitab  ANOVA table  MS = SS/df One-way ANOVA: SCORE versus HANDICAP Source DF SS MS F P HANDICAP Error Total

Technical conditions Normal populations  Normal probability plot for each sample Equal variances in the populations  Largest SD / smallest SD < 2 Independent observations  Random samples or randomized experiment

Example 2: Chip melting H0:  white =  semi-sweet =  butterscotch Ha: not all  i equal

Demo – ANOVA applet

Next Question: If do reject H 0, how can we decide which group means differ significantly from each other

Multiple Comparison Procedures How compare?