QUESTION 1

a) Ammonia in car exhaust. 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 daily ammonia concentrations (parts per million) on eight randomly selected

days during afternoon drive-time in the summer of a recent year.

1.53

1.50

1.37

1.51

1.55

1.42

1.41

1.48

i. Find the mean daily ammonia level in air in the tunnel.

ii. Find the median ammonia level.

iii. Interpret the values obtained in parts i and ii.

iv. Find the range of the ammonia levels.

v. Find the variance of the ammonia levels.

vi. Find the standard deviation of the ammonia levels.

vii. Suppose the standard deviation of the daily ammonia levels during morning drive-time at the exit ramp is 1.45 ppm. Which time, morning or afternoon drive time, has more variable ammonia levels?