1. A sample of 49 kitchens with gas cooking appliances were monitored during a one-week
period. The sample mean CO2level (ppm) was 624.16. Assume the CO2 levels are
normally distributed with population standard deviation 164.13.
(a) Calculate a 95% confidence interval for the true average CO2 level. Give answers to
2 decimals.
(b) What sample size is needed to ensure a width of 50ppm for a 95% confdence interval?