Explore BrainMass

# Confidence Interval for Mean & Line chart

Not what you're looking for? Search our solutions OR ask your own Custom question.

This content was COPIED from BrainMass.com - View the original, and get the already-completed solution here!

Find a confidence interval for µ assuming that each sample is from a normal population.
a. x-bar = 24, s = 3, n = 7, 90 percent confidence
b. x-bar = 42, s = 6, n = 18, 99 percent confidence
c. x-bar = 119, s = 14, n = 28, 95 percent confidence

A random sample of 16 pharmacy customers showed the waiting times below (in minutes). Find a 90 percent confidence interval for &#956;, assuming that the sample is from a normal population.

21 22 22 17 21 17 23 20
20 24 9 22 16 21 22 21

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

(a) Construct a 95 percent confidence interval for the true mean number of steps Dave takes on his run.

(b) What sample size would be needed to obtain an error of ± 20 steps with 95 percent confidence?

(c) Using Excel, plot a line chart of the data. What does the data suggest about the pattern over time?

See attached file for problems.