| PrisonStress | R Documentation |
This dataset gives the PSS (stress measurement) for 26 people in prison at the entry and at the exit. Part of these people were physically trained during their imprisonment.
data(PrisonStress)
A dataframe with 26 rows and 4 columns.
| [,1] | Subject | factor | anonymous subjects |
| [,2] | Group | factor | sport or control |
| [,3] | PSSbefore | numeric | stress measurement before training |
| [,4] | PSSafter | numeric | stress measurement after training |
Private communication. Charlotte Verdot, CRIS, Lyon 1 University, FRANCE
Verdot, C., Champely, S., Massarelli, R. and Clement, M. (2008) Physical activities in prison as a tool to ameliorate detainees mood and well-being. International Review on Sport and Violence, 2.
data(PrisonStress)
# The two groups are not randomized!
# The control group is less stressed before the experiment
with(PrisonStress,boxplot(PSSbefore~Group,ylab="Stress at the eginning of the study"))
# But more stressed at the end!
with(PrisonStress,boxplot(PSSafter~Group,ylab="22 weeks later"))
# So the effects of physical training seems promising
with(PrisonStress,plot(paired(PSSbefore,PSSafter),groups=Group,type="BA",facet=FALSE))
# Testing using gain scores analysis
difference<-PrisonStress$PSSafter-PrisonStress$PSSbefore
t.test(difference~PrisonStress$Group,var.equal=TRUE)
# Testing using ANCOVA
lmJail<-lm(PSSafter~PSSbefore*Group,data=PrisonStress)
anova(lmJail)
# Testing using repeated measures ANOVA
PSS<-c(PrisonStress$PSSbefore,PrisonStress$PSSafter)
Time<-factor(rep(c("Before","After"),c(26,26)))
Subject<-rep(PrisonStress$Subject,2)
Condition<-rep(PrisonStress$Group,2)
aovJail<-aov(PSS~Condition*Time+Error(Subject))
summary(aovJail)