Dave the jogger runs the same route every day about 22 miles

Dave the jogger runs the same route every day (about 2.2 miles). On 18 consecutive days, he recorded the number of steps using a pedometer. The results were

Construct a 95% confidence interval for the true mean number of steps Dave takes on his run. (Round your answers to 4 decimal places.)

Solution

The degree of freedom =n-1=18-1=17

Given a=1-0.95=0.05, t(0.025, df=17) =2.1098 (from student t table)

So the lower bound is

xbar -t*s/vn =3278.72 -2.1098*97.05/sqrt(18) =3230.459

So the upper bound is

xbar +t*s/vn =3278.72 +2.1098*97.05/sqrt(18) =3326.981