Practice Problems (Estimation)
1. Theodore is the owner of FlightPro (an app that provides maps and real-time weather reports for pilots) and is not satisfied with the map download speeds on electronic devices (μ = 90 seconds, σ = 30 seconds, normally distributed). So, he hires a software developer to reprogram the map feature in FlightPro with the hope that map download speeds will decrease to at least an average of 60 seconds. After the software update, Theodore takes a sample of 9 electronic devices to see how long a map of the Las Vegas airspace takes to download.
After the software update, you do not know the new population mean of FlightPro map download speeds on electronic devices, but you do know that the standard deviation after the software update remained 30 seconds.
a. Based on a mean download speed from 9 electronic devices being 60 seconds after the software update, what is the 90% confidence interval for the new average download speed of maps in FlightPro? Explain your results. Is the population mean before the software update captured within the confidence interval?
b. Based on a mean download speed from 9 electronic devices being 60 seconds after the software update, what is the 95% confidence interval for the new average download speed of maps in FlightPro? Explain your results. Is the population mean before the software update captured within the confidence interval?
c. Based on a mean download speed from 9 electronic devices being 60 seconds after the software update, what is the 99% confidence interval for the new average download speed of maps in FlightPro? Explain your results. Is the population mean before the software update captured within the confidence interval?