The Metropolitan Bus Company claims that the mean waiting time for a bus during rush hour is less than 5 minutes. A random sample of 20 waiting times has a mean of 3.7 minutes with a standard deviation of 2.1 minutes. At α = 0.01, test the bus company's claim. Assume the distribution is normally distributed.
3.70-5.00/(2.10/sqrt of 20. The answer to this equation is -2.77
So according to the standard normal table my answer at 1% significance level would be -2.33