A study by Bechtel, et al., 2009, in the Archives of Environmental & Occupational Health considered polycyclic aromatic hydrocarbons and immune system function in beef cattle. Some cattle were near major oil- and gas-producing areas of western Canada. The mean monthly exposure to PM1.0 (particulate matter that is < 1 ?m in diameter) was approximately 7.1 ?g/m3 with standard deviation 1.5. Assume the monthly exposure is normally distributed.
(a) What is the probability of a monthly exposure greater than 9 ?g/m3?
(b) What is the probability of a monthly exposure between 3 and 8 ?g/m3?
(c) What is the monthly exposure level that is exceeded with probability 0.05?
(d) What value of mean monthly exposure is needed so that the probability of a monthly exposure greater than 9 ? g / m3 is 0.01?