problem-7.13

problem-7.13  To compute, we have
> Xbar = 9.5; s=1; n=15
> alpha=.1
> tstar = qt(1 - alpha/2, df = n-1)
> SE = s/sqrt(n)
> c(Xbar - tstar*SE, Xbar + tstar*SE)
[1] 9.045 9.955
    
We see that ten days is not in this interval.