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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:
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)
P 75.985 > boxplot(rate~group) 80 90 ● > is.factor(group)
 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)
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.
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
µ3 as the population mean heart rate of the
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