Question

Recently, commuters in Minneapolis have protested on social media, saying commuting time has increased due to a number of badly-designed construction projects on main roads into and out of the city. A random sample of 72 commuters revealed an average commuting time of 46.8 minutes with a standard deviation of 6.90 minutes.

If you were to calculate a 95% confidence interval, what value would you use for the critical value t*?

Question 12 options:

	1.645
	1.993
	1.994
	1.96

Question 13 (1 point)

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Recently, commuters in Minneapolis have protested on social media, saying commuting time has increased due to a number of badly-designed construction projects on main roads into and out of the city. A random sample of 72 commuters revealed an average commuting time of 46.8 minutes with a standard deviation of 6.90 minutes.

Calculate a 95% confidence interval for the true mean commute time for Minneapolis commuters.

Question 13 options:

	45.25 to 48.35
	45.18 to 48.42
	44.98 to 48.78
	44.55 to 49.03

Question 14 (1 point)

Recently, commuters in Minneapolis have protested on social media, saying commuting time has increased due to a number of badly-designed construction projects on main roads into and out of the city. A random sample of 72 commuters revealed an average commuting time of 46.8 minutes with a standard deviation of 6.90 minutes.

What would be a 99% confidence interval for the true mean commute time for Minneapolis commuters? (Hint: you'll have to find a new number to use for the critical value using the StatKey applet)

Question 14 options:

	(44.85, 48.75)
	(44.75, 48.85)
	(44.65, 48.95)
	(44.55, 49.05)

Answer 1

We need to construct the 95% confidence interval for the population mean \muμ. The following information is provided:

Sample Mean	46.8
Population Standard Deviation	6.9
Sample Size	72

The critical value for α=0.05 is z_c =1.96. The corresponding confidence interval is computed as shown below:

CI=(45.18, 48.42)  

We need to construct the 99% confidence interval for the population mean \muμ. The following information is provided: Sample Mean 46.8 Population Standard Deviation 6.9 Sample Size 72 The critical value for α=0.05 is z_c =1.96. The corresponding confidence interval is computed as shown below:

CI = (44.75,48.85)​