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Unformatted text preview: = µi + ￿ij n = 45 women (all dog lovers) where µi is the group i mean. • If there’s only 2 levels, like in sex, then we can use a two-sample t-test H0 : µ1 = µ2. • If we have more than 2 levels, we extend this t-test idea to do a 1-way ANOVA. • A two-sample t-test is essentially a 1-way ANOVA (it’s the simplest one, there’s only 2 levels to the factor) 3 Each woman randomly assigned to one of three treatment groups as: 1) alone 2) with friend 3) with pet Their heart rate is taken and recorded during a stressful task. Allen, Blascovich, Tomaka, Kelsey, 1988, Journal of Personality and Social Psychology. 4 > pets=read.csv("pets.csv") 100 > head(pets) group rate 1 P 69.169 2 F 99.692 3 P 70.169 4 C 80.369 5 C 87.446 6 P 75.985 > boxplot(rate~group) 80 90 ● > is.factor(group) [1] TRUE 70 The treatment groups are: ‘C’ for control group or alone. ‘F’ for with friend. ‘P’ for with pet. 60 > attach(pets) Consider the distribution of heart rate by treatment group... C F P > table(group) group CFP 15 15 15 This is a balanced 1-way ANOVA since all groups have the same number of subjects. 5 Get the mean of each group. > tapply(rate,group,mean) C F P 82.52407 91.32513 73.48307 If we consider µ1 as the population mean heart rate of the control group, µ2 as the population mean heart rate of the friends group, µ3 as the population mean heart rate of the pet g...
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This note was uploaded on 06/12/2013 for the course MATHEMATIC MAT7870 taught by Professor Sun during the Winter '13 term at Wayne State University.

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