In a study of postmeningitic and postencephalitic brain damage, each subject was given a battery of tests, providing a composite score for each. Low scores for the composite measure presumably represented a considerable degree of residual brain damage. The subjects were divided into three groups according to type of initial infection and into three crossed groups according to time since apparent physical recovery from the illness. The data are below. Fill in the correct omega squared for each source of variance.
1-2 Years 3-5 Years 7-10 Years
Postencephalitic 71.7 62.25 50.00
Postmeningitic 82.0 79.25 60.0
Postoperative Control 71.75 81.75 89.75
SS df MS F omega squared
Type of Infection 2413.556 2 1206.778 14.224*
Time 536.222 2 268.111 3.16
Type x Time 2194.444 4 548.611 6.466*
Error 2290.75 27 84.843
*p<.05
What is the average variance within the groups? _______________ (put in a number)
What is the variability of the Type of Infection Means ignoring the effects of time? __ (put in a number)
How many subjects are in each group? _________________
What is the variance of the cell means around the grand mean after the variability due to the main effects has been removed. ___________________
?2 = ?2effect
?2total
?2A = (a-1)(MSinf-MSe)/nab ?2inf=
?2B = (b-1)(MStime-MSe)/nab ?2time=
?2AB = (a-1)(b-1)(MSinfxtime-MSe)/nab ?2infxtime=
?2total = ?2inf+ ?2time + ?2infxtime+ ?2error =
Complete subsequent Tukey Tests and LSD tests on all significant effects and state your conclusions. When conducting post hoc tests for the type of infection x Time interaction, examine the effects of type of brain damage at each level of time.
1-2 Years 3-5 Years 7-10 Years
Postencephalitic 71.7 62.25 50.00
Postmeningitic 82.0 79.25 60.0
Postoperative Control 71.75 81.75 89.75
Main Effect of Type of Infection
Interaction of Type of Infection x Time
1-2 years
3-5 years
7-10 years
Describe a main effect, simple effect and an interaction is and what the relationship between simple effects and interactions is?
