A group of statistics students decided to conduct a survey at
their university to find the average (mean) amount of time students
spend studying per week. Previous studies revealed an average of 20
hours per week with a standard deviation of 10 hours. Given a
sample of 144 students:

5. What is the probability of finding a sample mean less than 18
hours?
a. 0.4820
b. 0.4920
c. 0.0080
d. 0.0180

6. What is the probability that average student study time is
between 18 and 22 hours?
a. 0.9640
b. 0.0160
c. 0.0360
d. 0.9840