## HANDOUT 8.1

### RANDOMIZED RESPONSE

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 24 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 15 "a" responses, we
would subtract 12 from 15, leaving us with 3 people who received the
tails question and answered "a."

5. We can now assume that approximately 3 people who got the tails
question answered "a. " To get the percentage of people who got the tails question and answered "a, "we divide 3 by 12 (the number of
people who probably got the tails question). Thus, we estimate that
3/12 or 25% 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 the 24 students who
were cocaine users was approximately 25%.

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