Question

The average American city has 50 buses that use green energy, with a standard deviation of 5 buses. A city planner is interested in the sample mean number of buses for a sample of 30 cities. He calculates that: μx=μn−−√=5030−−√=9.13 and σx¯=σn−−√=530−−√=0.91 What did he do wrong?

Answer 1

$\mu_{\bar x}$ = $\mu$ = 50

$\sigma_{\bar x} = \sigma/\sqrt n$ = 5/$\sqrt 30$ = 0.9129