Question 8.108

77. Choose at random a person aged 19 to 25 years and ask, “In the past four days, how many days did you do physical exercise or work out?” Based on a large sample survey, here is a discrete probability model for the answer you will get:

# of Days 0 1 2 3 4
Probability 0.61 0.17 0.10 0.08 0.04
  1. What is the probability that the person you chose worked out either two or three days in the past four?
  2. What is the probability that the person you chose worked out at least one day in the past four?

77.

(a) The probability is .

(b) The complement to the event of working out at least one day is working out no days. Thus, using the complement rule, the desired probability is .