# Confidence Interval for Mean & Line chart

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 μ, 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.

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#### Solution Summary

The solution provides step by step method for the calculation of confidence interval for mean, sample size and line chart. Formula for the calculation and Interpretations of the results are also included. Interactive excel sheet is included. The user can edit the inputs and obtain the complete results for a new set of data.