Question

which of these is an example of a random sample?
a. customers buying a new cell phone are surveyed about cell phone plans.
b. a phone survey is conducted using twenty names randomly taken from the phone book.
c. every twentieth caller to an independent radio station receives tickets to a concert.
d. a phone plan company surveys people on the beach to see how well they are receiving service, and uses this information in future advertising.

Explanation:

A random sample is one where every member of the population has an equal chance of being selected. In option A, only customers buying a new cell - phone are surveyed, which is a biased sample related to a specific purchasing behavior. In option C, it's a systematic selection (every twentieth caller), not truly random. In option D, surveying people on the beach is a convenience sample and may not represent the entire customer base of the phone - plan company. Option B randomly selects names from the phone book, giving each listed individual an equal chance of being surveyed.

Answer:

B. A phone survey is conducted using twenty names randomly taken from the phone book.