Medical Marijuana. Refer to Exercise 8.77.

a. The mean number of days that 30 adolescents in substance abuse treatment used medical marijuana in the last 6 months was 105.43.

Find a 95% confidence interval for μ based on that data.

b. Compare the 95% confidence intervals obtained here and in Exercise 8.77

(a) by drawing a graph similar to Fig. 8.7 on page 366.

c. Compare the margins of error for the two 95% confidence intervals.

d. What principle is being illustrated?