In a certain population of smokers, the number of cigarettes smoked per day followed a fairly normal curve with a mean of 15 and a standard deviation of 6.
a. Use the 68-95-99.7 Rule to sketch a curve for this distribution, marking off the numbers of cigarettes smoked daily that are within 1, 2, and 3 standard deviations of the mean.
b. Explain why the lower end of the curve is not perfectly consistent with reality.
c. Find the z-score for a person who smokes one pack (20 cigarettes) a day.
d. Characterize one pack a day as being unusually low, unusually high, or not unusual.
e. Find the z-score for a person who smokes two packs a day.
f. Characterize two packs a day as being unusually low, unusually high, or not unusual.