Is the concentration of ultrafine particles dangerous? In Kansas City, Missouri, suppose fifteen 24-hour periods are selected at random and the concentration of ultrafine particles is carefully measured over each period. The summary statistics are x‾ = 10.76 mg/m3 and s = 4.7 μg/m3 .
a. Find a 95% confidence interval for the true mean level of ultrafine particles in a 24-hour period in Kansas City.
b. Is there any evidence to suggest that the mean level of ultrafine particles in a 24-hour period in Kansas City is over the EPA standard of 35 μg/m3?