Estimation
A researcher wants to estimate the average time spent by people on a new app. A sample of 200 users showed an average usage time of 15 minutes with a standard deviation of 3 minutes. What is the 90% confidence interval for the average usage time on the app?
A sample of 150 students was taken, and their average score on a standardized test was 85 with a standard deviation of 10. What is the standard error of the mean for this sample?
A sample of 80 cars showed an average fuel efficiency of 30 miles per gallon with a standard deviation of 3 miles per gallon. What is the margin of error for a 99% confidence interval for the population mean fuel efficiency?
You have a sample of 100 observations with a sample mean of 50 and a standard deviation of 10. What is the standard error of the mean?
You have a sample of 50 observations with a sample mean of 75 and a standard deviation of 5. Construct a 95% confidence interval for the population mean.