You sample for carbon monoxide TWA exposure in a work area on 12 randomly chosen days with the following results (in chronological order): 21, 27, 18, 32, 37, 20, 12, 35, 41, 30, 16, 25 ppm

a. Using a graphical approach on log-normal probability paper, plot the data and find the GM and GSD.

b. Based on the above calculations, what is the probability that on any one day the concentration will exceed 50 ppm?