A researcher wished to estimate the fraction of students in a large high school who have used illegal drugs on at least one occasion. He carried out his survey through interviews with students. To satisfy legal and ethical guidelines, it was necessary to interview students only when a parent was present. Only eight students showed up to participate.

a. Is this study likely to yield a biased estimate of illegal drug use or an unbiased estimate? Why?

b. What effect does such a small sample size have on sampling error of an estimate, compared with a larger sample?