1. Flip a coin. If it comes up heads, answer the "heads " question. If comes up tails, answer the "tails " question. Put your answer (a or b) here _______.
Heads question: Are you a college student?a. Yes
b. No
Tails question: Have you used cocaine in the last two months?
a. Yes
b. No
2. Suppose we give this survey to 200 college students. How many will get the "heads " question? ____
3. How will they answer? ____ Are we interested in their responses?
4. Given that we are not interested in their answers, we can subtract out their responses. Thus, if we received a total of 110 "a" responses, we would subtract 100 from 110, leaving us with 10 people who received the tails question and answered "a."
5. We can now assume that approximately 10 people who got the tails question answered "a. " To get the percentage of people who got the tails question and answered "a, "we divide 10 by 100 (the number of people who probably got the tails question). Thus, we estimate that 10/100 or 10% of the people who got the tails question answered "a. "
6. Since there is no reason to assume that the people who got the "tails " question are any different from those who got the "heads " question, we would assume that the percentage of cocaine users in our sample of 200 students was approximately 10%.