# A tibble: 1 × 3
xbar sx n
<dbl> <dbl> <int>
1 118. 81.5 30

What is an approximate 95% confidence interval for the mean air time in flights using the normal curve?

01:00

An economist aims to estimate the average weekly cost of groceries per household in two cites: Oakland, CA (population ~400,000) and Fremont, CA (population ~200,000). Both of these populations of households are presumed to have a similar standard deviation of weekly grocery costs. The economist takes a simple random sample (without replacement) of 100 households from each city, records their costs, and computes a 95% confidence interval for the average weekly cost.

Approximately how much wider would Oakland’s confidence interval be than Fremont’s?

01:00

An economist aims to estimate the average weekly cost of groceries per household in two cites: Grimes, CA (population ~400) and Tranquility, CA (population ~800). Both of these populations of households are presumed to have a similar standard deviation of weekly grocery costs. The demographer takes a simple random sample (without replacement) of 100 households from each city, records their costs, and computes a 95% confidence interval for the average weekly cost.

Approximately how much wider would Tranquility’s confidence interval be than Grimes’s?

02:00

What will happen to the shape of the empirical distribution as we increase \(n\)?

01:00

What will happen to the shape of the sampling distribution as we increase \(n\)?