An article reported that for a sample of 50 kitchens with ga

An article reported that for a sample of 50 kitchens with gas cooking appliances monitored during a one-week period, the sample mean CO_2 level (ppm) was 654.16, and the sample standard deviation was 164.04. Calculate and interpret a 95% (two-sided) confidence interval for true average CO_2 level in the population of all homes from which the sample was selected. (Round your answers to two decimal places.) Suppose the investigators had made a rough guess of 173 for the value of s before collecting data. What sample size would be necessary to obtain an interval width of 44 ppm for a confidence level of 95%? (Round your answer up to the nearest whole number.)

Solution

Ci is (608.69,699.63)

sample size=(1.96*sd/E)^2

sd=173

E=margin of error=45.4687

sample size=55.61 so approximately 56.