What is the probability of being in the youngest or oldest age categories and having a preference for positive hair styling ads?

• A. 4%
• B. 6%
• C. 8%
• D. 10%

Answer: (B)

Think about the joint probability of two events: being in a youngest or oldest age category and having a preference for positive hair styling ads. Since being in the youngest age group and being in the oldest age group are mutually exclusive, you add the probabilities for each combination that includes a positive ad preference: P(youngest and positive) plus P(oldest and positive). If you’re using a table, read off the two relevant cells, sum them, and divide by the total to get the probability. For example, if the youngest–positive cell is 4% of respondents and the oldest–positive cell is 2%, their sum is 6%, which is the requested probability.