According to the website Righting Injustice.com, about 77% of all underground storage tanks, or USTs, have “confirmed releases” or leaks. Researchers in California want to know if the percentage is lower in their state. To do this, they randomly sample 47 service stations in California and determine whether there is any evidence of leakage. In their sample, 33 of the stations exhibited leakage. Is there evidence that the California percentage is really lower?

a) What are the null and alternative hypotheses?
b) Check the assumptions necessary for inference.
c) Test the null hypothesis.
d) What do you conclude (in plain English)?
e) If California’s percentage is actually lower, have you made an error? What kind?
f) What two things could you do to decrease the probability of making this kind of error?
g) What are the advantages and disadvantages of taking those two courses of action?