Jason sampled 60 smokers who were questioned about the number of hours they sleep each day. Jason wants to test the hypothesis that the smokers need less sleep than the general public which needs an average of 7.5 hours of sleep with a population standard deviation of 0.7 hours. If the sample mean is 7.2 hours, what is the z-score? Answers are rounded to the hundredths place.

• a.)-0.33
• b.)0.67
• c.)2.67
• d.)-3.32