Question: Three-way catalytic converters have been installed in new vehicles in order to reduce pollutants from motor vehicle exhaust emissions. However, these converters unintentionally increase the level of ammonia in the air. Environmental Science & Technology (Sept. 1, 2000) published a study on the ammonia levels near the exit ramp of a San Francisco highway tunnel. The data in the table represent the daily ammonia concentration (parts per million, or ppm) on eight randomly selected days during the afternoon drive time in the summer of recent years.

(a) Find the variance.

(b) Find the standard deviation.

(c) Find Q1, Q2, and Q3.

(d) Put the data into a boxplot, listing the “5# summary”.

(e) Assume from historical evidence that the mean daily ammonia level in San Francisco during the summer time is 1.52 ppm with a standard deviation of 0.04 ppm. If you observed (on one summer afternoon) the ammonia level to be 1.62 ppm, would that be considered a usual, unusual, or very unusual data point? How do you know? Show your work.