chumho

Hi,

I have found the p-values from the solutions are double of what I did using R. Here's the answers from the solution manual:

5.2
(a) 0.085, do not reject H0.
(b) 0.003, reject H0.
(c) 0.438, do not reject H0.
(d) 0.042, reject H0.

These are what I got using R:
pval.a <- pt(1.91, df=11-1,lower.tail = F)
print(pval.a)
# reject H0 as pval.a=0.0426<alpha

# b
# one-sided, reject region is the lower tail
pval.b <- pt(-3.45, df=17-1,lower.tail = T)
print(pval.b)
# reject H0 as pval.b=0.0016<alpha

# c
# two-sided, reject region is either the lower or upper tail
# bc t-statistic is > 0, lower.tail = F
pval.c <- pt(0.83, df=7-1, lower.tail = F)
print(pval.c)
# 0.219 > alpha/2
# Failed to reject the H0

# d
# one-sided. t-statistic>0, lower.tail = F
pval.d <- pt(2.13, df=28-1,lower.tail = F)
print(pval.d)
# reject H0 as pval.a=0.021<alpha

Thanks,
Eric.

chumho

Forgot to mention it is for Intro. Statistics for biomedical sciences.

JulieVu

Hi Eric,

Thanks for submitting these corrections. The p-values for parts a), b), and d) should indeed be the one-sided p-values (0.0426, 0.00165, 0.0212). The one for part c) should equal 0.438.