coils=read.csv("https://webpages.uidaho.edu/~renaes/Data/coils.csv",header=T)
View(coils)

boxplot(selfind~temp,data=coils)
boxplot(selfind~coil,data=coils)

# temp and coils are numeric so we have to tell R that they are factors
# or we get the wrong results (check df for treatment and block to see
# dftrt = t-1 and dfblock = b-1

# without using factor() for the factors
# results are incorrect
fail=aov(selfind~temp+coil,data=coils)
summary(fail)
# this is THE good analysis :-)
fit=aov(selfind~factor(temp)+factor(coil),data=coils)
summary(fit)
# analysis without block
noblock=aov(selfind~factor(temp),data=coils)
summary(noblock)

trt.means=tapply(coils$selfind,coils$temp,mean,na.rm=T)
blk.means=tapply(coils$selfind,coils$coil,mean,na.rm=T)

res=rstudent(fit)
yhat=fitted(fit)

hist(res,main='Residuals')
# with so few data points, a boxplot might be better
boxplot(res,main='Residuals')
plot(yhat,res,main='Predicted vs. Residuals')
abline(0,0)
qqnorm(res,xlim=c(-3,3),ylim=c(-3,3)); qqline(res)