statistics
posted by Hannah on .
Most Americans, 67% in fact, say frequent handwashing is the best way to fend off the flu. Despite that, when using public restrooms, women wash their hands only 66% of the time and men wash only 43% of the time. Of the adults using the public restroom at a large grocery chain store, 58% are women. What is the probability that the next person to enter the restroom in this store washes his or her hands? (Enter your answer to two decimal places.)

Use a probability tree:
Next person
male: 42% wash his hands: 43%
female: 58% wash her hands 66%
P(wash)=42%*43% + 58%*66%
=0.5634