Question 7.105

105. Carbon Dioxide Concentration. The Carbon Dioxide Information Analysis Center (cdiac.ornl.gov/pns/current_ghg.html) reported in 2014 that the mean concentration of the greenhouse gas carbon dioxide is 397 parts per million (ppm). Suppose the population is normally distributed, assume that the standard deviation is 25 ppm, and suppose we take atmospheric samples from 25 cities.

  1. Calculate the probability that the sample mean carbon dioxide concentration will be between 387 and 407 ppm.
  2. Which sample mean represents the median sample mean? Explain how you know this.
  3. Find the two symmetric sample mean carbon dioxide concentrations containing the middle 99% of all sample means.

7.1.105

(a) 0.9544 (b) 397 ppm; in a normal distribution the median equals the mean. (c) 384.12 ppm and 409.88 ppm