Researchers at a pharmaceutical company have found that the effective time duration of a safe dosage of a pain relief drug is normally distributed with mean 2 hours and standard deviation of 0.20 hours. For a patient selected at random:
(a) What is the probability that the drug will be effective for 2 hours or less?
(b) What is the probability that the drug will be effective for 1.5 hours or more?
(c) Find the standard error of the mean for a sample of 25 patients.
(d) Find the probability that the average effective time of the pain relief drug for a sample of 25 patients is between 1.95 hours and 2.05 hours.