Cigarette Smoking A researcher found that a cigarette smoker smokes on average

31

cigarettes a day. She feels that this average is too high. She selected a random sample of

10

smokers and found that the mean number of cigarettes they smoked per day was

28

. The sample standard deviation was

2.7

. At

=0.05

, is there enough evidence to support her claim? Assume that the population is approximately normally distributed. Use the critical value method and tables.