(580-600)/(sqrt(30*1.5^2))
pnorm(-2.43)
1-pnorm(-2.43)
pt(2)
pt(2, 15)
1 - pt(2, 15)
qt(.95)
qt(.95, 15)
sqrt(8.3^2/13 + 7.7^2/14)
70.3-72.7
-2.4/3.09
qt(.975, 12)
exam = read.csv("exam1R.csv")
exam
attach(exam)
score
sex
ime
prezime
females=score[sex =="F"]
females
males=score[sex =="M"]
males
mean(females)
mean(males)
sd(females)
sd(males)
length(males)
length(females)
tnumer = mean(males) - mean(females)
tnumer
tdenom = sqrt(var(females)/length(females) + var(males)/length(males))
tdenom
t = tnumer/tdenom
t
pt(-0.779, 12)
t.test(males, females)
t.test(score~sex)
?t.test
t.test(score~sex, var.equal=T)
poolvar = (length(males)-1)*var(males) + (length(females) -1)*var(females)
poolvar
poolvarfinal = poolvar/(length(males) + length(females) - 2)
poolvarfinal
poolsd = sqrt(poolvarfinal)
poolsd
tdenom = 7.972*sqrt(1/length(males) + 1/length(females))
t= tnumer/tdenom
t
t.test(score~sex, var.equal = T)
pt(-.781, 25)
2*pt(-.781, 25)