Answers
> x=c(0.54,-3.67,1.41,23.51,20.77,15.9,16.7,2.48,12.27,2.64,
+ 22.12,14.03,17.8)
>
> y=c(21.22,12.61,15.04,14.51,10.91,-4.9, 22.71)
>
> # a) The mean of x is
> Xbar=mean(x)
> Xbar
[1] 11.26923
>
> # b) Variance of Xbar is
>
> V.Xbar=8.3^2/length(x)
> V.Xbar
[1] 5.299231
>
> # c) The mean of Y is
> Ybar=mean(y)
> Ybar
[1] 13.15714
>
> # d) Variance of Ybar is
>
> V.Ybar=10.1^2/length(y)
> V.Ybar
[1] 14.57286
>
> # e) Var of Xbar-Ybar is
>
> V.dif=V.Xbar+V.Ybar
> V.dif
[1] 19.87209
>
>
> # f) The critical value for 96% Confidence interval of \muX-\muY is
> z=qnorm(.98, 0,1)
> z
[1] 2.053749
>
> # g) 96% CI for \muX-\muY
> Lower_limit=Xbar-Ybar-z*sqrt(V.dif)
> Lower_limit
[1] -11.04314
>
> Upper_limit=Xbar-Ybar+z*sqrt(V.dif)
> Upper_limit
[1] 7.267314
>
>
> # h) Length of 96% CI is
>
> Length=Upper_limit-Lower_limit
> Length
[1] 18.31045
>
> ## i) The p-value for \muX-\muY>0
>
> P.value=pnorm((Xbar-Ybar)/sqrt(V.dif), 0,1)
> P.value
[1] 0.3359629
## k)
x=c(0.54,-3.67,1.41,23.51,20.77,15.9,16.7,2.48,12.27,2.64,
22.12,14.03,17.8)
y=c(21.22,12.61,15.04,14.51,10.91,-4.9, 22.71)
# a) The mean of x is
Xbar=mean(x)
Xbar
# b) Variance of Xbar is
V.Xbar=8.3^2/length(x)
V.Xbar
# c) The mean of Y is
Ybar=mean(y)
Ybar
# d) Variance of Ybar is
V.Ybar=10.1^2/length(y)
V.Ybar
# e) Var of Xbar-Ybar is
V.dif=V.Xbar+V.Ybar
V.dif
# f) The critical value for 96% Confidence interval of \muX-\muY is
z=qnorm(.98, 0,1)
z
# g) 96% CI for \muX-\muY
Lower_limit=Xbar-Ybar-z*sqrt(V.dif)
Lower_limit
Upper_limit=Xbar-Ybar+z*sqrt(V.dif)
Upper_limit
# h) Length of 96% CI is
Length=Upper_limit-Lower_limit
Length
## i) The p-value for \muX-\muY>0
P.value=pnorm((Xbar-Ybar)/sqrt(V.dif), 0,1)
P.value