Lesson 6.4 Name_________________________________________

Conditional Probability Hour_____

Suppose there a population that 0.1% of all individuals have a disease. The presence of the disease cannot be determined by outward appearances, but there is a diagnostic test available. Unfortunately the test is not infallible: 80% of those with positive test have the disease; the other 20% who show positive results are false-positive.

E = event that the individual has the disease

F = event that the individuals diagnostic test is positive

What is the _______

What is the , given that F has occurred. __________

Conditional Probability -

	Nondefective	Defective	Total
Company 1	10	5	15
Company 2	8	2	10
Total	18	7	25

A GFI (ground fault interrupt) switch turns off power to a system in the event of an electrical malfunction. A spa manufacturer currently has 25 spas in stock, each equipped with a single GFI switch. Two different companies supply the switches, and some of the switches are defective, as summarized in the following table:

Let E = event that GFI switch selected is from Company 1

Let F = event that GFI switch selected is defective

_____ _______ _______

Now suppose the testing reveals a defective switch. How likely is the switch came from

Company 1 ?

Consider the population of all families with two children. Representing the gender of each child using G for girl and B for boy results in four possibilities: BB BG GB GG