13 The article Gas Cooking Kitchen Ventilation and Exposure to Combustion Products Indoor Air 2006 65 73 reported that for a sample of 50 kitchens with gas cooking appliances monitored during a one week period the sample mean CO level ppm was 654 16 and the sample standard deviation was 164 43 a Calculate and interpret a 95 two sided confidence interval for true average CO level in the population of all homes from which the sample was selected b Suppose the investigators had made a rough guess of 175 for the value of s before collecting data What sample size would be necessary to obtain an interval width of 50 ppm for a confidence level of 95