Exercises: Analyze Decisions and Strategies Using Probability
Work through each section in order. For testing problems, build the two-way table over the stated population and compute the decision-relevant quantity by counting. Remember the difference between a test's accuracy P(positive | disease) and the decision-relevant P(disease | positive). For strategy problems, account for how a choice changes ALL of the probabilities, not just the one you want. Write explanation answers in complete sentences and name your assumptions.
Warm-Up: Tools You Already Have
These problems review expected value and conditional probability, the tools this lesson combines.
In a population of people, a two-way table shows people have a condition and test positive, while people do NOT have the condition but also test positive. Among all who test positive, how many actually have the condition? ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ And how many test positive in total? ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲ ̲