Pregnant 70 4 74 Not Pregnant 5 14 19 Total 75 18 93 Since we are given the woman is not pregnant, we are limited to the 19 women in the not pregnant row, of which 5 had a positive test. This gives: Negative Positive Test Total Test Pregnant 70 4 74 5 14 19 Not Pregnant Total 75 18 93 This result is referred to as a false positive: A positive test result when the woman is not actually pregnant. In this section we have learned empirical probability. In the next section we will discuss another kind of probability that you may be familiar with theoretical – probability. Exercises 4.1 A professor gave a test to students in a morning class and the same test to the afternoon class. The grades are summarized below. Use the table for questions 1-2. If one student was chosen at random, find each probability: A B C Total P(in the morning class) P(earned a C) Morning Class 8 18 13 39 P(earned an A and was in Afternoon Class 10 4 12 26 the afternoon class) P(earned an A given the Total 18 22 25 65 student was in the morning class) What is the probability that a student who earned a B was in the afternoon What’s the probability that a student in the afternoon class earned a B? Explain the difference between these two quantities. The contingency table below shows the number of credit cards owned by a group of individuals below the age of 35 and above the age of 35.
Pregnant 70 4 74 Not Pregnant 5 14 19 Total 75 18 93 Since we are given the woman is not pregnant, we are limited to the 19 women in the not pregnant row, of which 5 had a positive test. This gives: Positive Test Negative Test Total Pregnant 70 4 74 Not Pregnant 5 14 19 Total 75 18 93 This result is referred to as a false positive: A positive test result when the woman is not actually pregnant. In this section we have learned empirical probability. In the next section we will discuss another kind of probability that you may be familiar with – theoretical probability. Exercises 4.1 A professor gave a test to students in a morning class and the same test to the afternoon class. The grades are summarized below. Use the table for questions 1-2. If one student was chosen at random, find each probability: P(in the morning class) P(earned a C) P(earned an A and was in the afternoon class) P(earned an A given the student was in the morning class) A B C Total Morning Class 8 18 13 39 Afternoon Class 10 4 12 26 Total 18 22 25 65 What is the probability that a student who earned a B was in the afternoon What’s the probability that a student in the afternoon class earned a B? Explain the difference between these two quantities. The contingency table below shows the number of credit cards owned by a group of individuals below the age of 35 and above the age of 35.
Chapter4-Probability9-7-18.docx