You move to a new town and want to decide on when to start for work. You do not

Question

You move to a new town and want to decide on when to start for work. You do not want to reach too early and not be too late too many times. You, thus, collected data for 10 days and obtained an average of 34.5 minutes. You took the standard deviation of 4.5 minutes from a commuting friend and believe that that is the standard deviation for the area. Prepare a 95% confidence interval for the true average commuting time. Please use Excel. You move to a new town and want to decide on when to start for work. You do not want to reach too early and not be too late too many times. You, thus, collected data for 10 days and obtained an average of 34.5 minutes. You took the standard deviation of 4.5 minutes from a commuting friend and believe that that is the standard deviation for the area. Prepare a 95% confidence interval for the true average commuting time. Please use Excel.

Explanation / Answer

o calculate the confidence interval for a population mean, the returned Confidence value must then be added to, and subtracted from, the sample mean. I.e. for the sample mean x:

Confidence Interval =   x bar ± CONFIDENCE

Formula:

=CONFIDENCE.T(0.05,4.5,10)

Result:

3.219106

Confidence Interval =   x bar +confidence

=34.5-3.219106 and 34.5+3.219106

=31.28,37.72

lower limit=31.28

upper limit=37.72

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