A marketing research company was asked to determine how much money teenagers (ages 13 - 19) spend on recorded music (cassette tapes, CDs and records). The company randomly selected 80 malls located around the country. A field researcher stood in a central location in the mall and asked passers-by who appeared to be the appropriate age to fill out a questionnaire. A total of 2,050 questionnaires were completed by teenagers. On the basis of this survey, the research company reported that the average teenager in this country spends $155 each year on recorded music.

Listed below are several statements concerning this survey. Place a check by every statement that you agree with.

a) The average is based on teenagers' estimates of what they spend and therefore could be quite different from what teenagers actually spend.

b) The sample of 2,050 teenagers is too small to permit drawing conclusions about the entire country.

c) They should have asked teenagers coming out of music stores.

d) The average could be a poor estimate of the spending of all teenagers given that only teenagers in malls were sampled.