Back to Find conditional probability from a model — Problem 5 · Task Set 23
Exercises: Find Conditional Probability as the Fraction of B's Outcomes That Are Also A
Work through each section in order. To find P(A | B), restrict to B's outcomes first, then count how many of them are also in A: the denominator is the number of B's outcomes, NOT all outcomes. Write probabilities as fractions in lowest terms unless asked otherwise, and interpret each conditional probability with a sentence: "among the B's, this fraction are A."
Grade 10·20 problems·~32 min·Common Core Math - HS Statistics and Probability·group·hss-cp-b-6
Work through problems with immediate feedback
A
Fluency Practice
For each, restrict to B and count A among B's outcomes. Enter probabilities as fractions in lowest terms (for example, 1/3).
1.
A survey of 40 people is summarized in the two-way table. Conditioning on a row or column restricts to that group.
| Coffee | Tea | Total | |
|---|---|---|---|
| Adult | 18 | 6 | 24 |
| Teen | 4 | 12 | 16 |
| Total | 22 | 18 | 40 |
Find — among adults, the fraction who prefer coffee. Enter your answer as a fraction in lowest terms.