Question

9. Effect size and ANOVA Aa Jackie Andrade, a psychology professor at the University of Plymouth, conducted a study regarding the impact on attention of simple activities such as doodling. She found that research participants who doodled while listening to a conversation were able to recall more details of the conversation than those who were not doing anything. You decide to explore this issue by having three different groups try recalling details from a conversation. The firs group is doing a math problem, the second group is not doing anything, and the third group is doodling The sample mean and sum of squares of the scores for each of the three groups are presented in the following table. Group Sample Mean Sum of Squares 91.6 93.7 09.8 4,570.5600 4,907.7600 5,472.2400 No acthit)y Math problem After collecting the data, you analyze the data using an ANOVA. The results of your analysis are presented in the following ANOVA table. ANOVA Table Source of 4,957.17 14,950.56 19,907.73 MS 2,478.59 207.65 Within Treatments 72 These findings are significant at α-.01, which tells you that the difference is very unlikely to have occurred just by chance, but it does not tell you the size of the effect. A simple measure of the effect size is given by Complete? Chapter 12 Problem Set ,957.1 4.,950.56 19,907.73 2,478.59 207.65 1-94 Within Treatments 72 Total These findings are signficant at α .01, which tels you that the difference is very unlikely to have occurred just by chance, but it does not tell you the size of the effect. A simple measure of the effect size is given by What is the formula for this measure of the effect size? Tukey's honestly signdcane diterence test 11.94 3,965.74 096 11.94% 25% 3,965.74% 0.25 Based on the data given, the effect size is (Round your answer to two decimal places) The percentage of variability in the scores accounted for by the effect due to treatments is

Answer 1

Solution: These findings are significant at
α 0.01
, which tells you that the difference is very unlikely to have occurred just by chance, but it does not tell you the size of the effect. A simple measure of the effect size is given by $\eta^{2}$

What is the formula for this measure of the effect size?

Answer:
SSbetween/SStotal

Based on the data given, the effect size is 0.25

The percentage of variability in the scores accounted for by the effect due to treatment is 25%