20. Using Composite Water Samples The Orange County Department of Public Health tests water for contamination due to the presence of E. coli (Escherichia coli) bacteria.

To reduce laboratory costs, water samples from six public swimming areas are combined for one test, and further testing is done only if the combined sample fails.

Based on past results, there is a 2% chance of finding E. coli bacteria in a public swimming area. Find the probability that a combined sample from six public swimming areas will reveal the presence of E. coli bacteria.

Conditional Probabilities. In Exercises 21–24, use the following data from the 100 Senators from the 108th Congress of the United States.

4-5 Multiplication Rule: Complements and Conditional Probability 173 Republican Democrat Independent Male 46 39 1 Female 5 9 0