An article reported that for a sample of 40 kitchens with gas cooking appliances

Question

An article reported that for a sample of 40 kitchens with gas cooking appliances monitored during a one-week period, the sample mean coz level (ppm) was 654.16, and the sample standard deviation was 166.42. (a) Calculate and interpreta 95% (two-sided) confidence interval for true average coz level in the population of all homes from which the sample was selected. (Round your answers to two decimal places.) ( 600.93%, 707.39%) ppm Interpret the resulting interval. o We are 95% confident that the true population mean lies above this interval. o We are 95% confident that this interval does not contain the true population mean. o we are 95% confident that this interval contains the true population mean. o We are 95% confident that the true population mean lies below this interval. (b) Suppose the investigators had made a rough guess of 174 for the value of s before collecting data. What sample size would be necessary to obtain an interval width of 43 ppm for a confidence level of 95%? (Round your answer up to the nearest whole number.) 252 V kitchens

Explanation / Answer

The statistical software output for this problem is:

One sample T summary confidence interval:
: Mean of population

95% confidence interval results:

Hence,

95% confidence interval will be:

(600.94, 707.38) ppm

Mean Sample Mean Std. Err. DF L. Limit U. Limit 654.16 26.313312 39 600.9363 707.3837

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