Question 207136
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: 
3,450 3,363 3,228 3,360 3,304 3,407 3,324 3,365 3,290
3,289 3,346 3,252 3,237 3,210 3,140 3,220 3,103 3,129
1st: Find the mean (x-bar) and the standard deviation (s) of your data set.
----------------------- 
(a) Construct a 95 percent confidence interval for the true mean number of steps Dave takes on his run.
2nd Calculate the standard error:
E = 1.96*(s/sqrt(18)
---
3rd: 
95% CI: x-bar - E < u < x-bar + E
========================================= 
 
(b) What sample size would be needed to obtain an error of ± 20 steps with 95 percent confidence? 
Since E = 1.96[s/sqrt(n)], n = [1.96s/E]^2
=========================================
Cheers,
Stan H.