Name:
Ch 11.2 Conditional Probability Practice
Let S, C, W, and R represent sunny, cloudy, windy, and rainy weather respectively. Use probability notation to
describe each event.
1) The chance of rainy weather
2) The chance of rainy weather if it is windy
3) The chance of windy weather if it is sunny
4) The chance of sunny and windy weather
The tree diagram given shows probabilities concerning a disease and a medical test used to detect it. Find each
probability.
5) P(D) =
D = the person has the disease
6) P( P I D) =
H = the person is healthy
7) P(D and P) =
P = the person tested positive
8) P(H and P) =
N = the person tested negative
Name:
Ch 11.2 Conditional Probability Practice
Let S, C, W, and R represent sunny, cloudy, windy, and rainy weather respectively. Use probability notation to
describe each event.
1) The chance of rainy weather
2) The chance of rainy weather if it is windy
3) The chance of windy weather if it is sunny
4) The chance of sunny and windy weather
The tree diagram given shows probabilities concerning a disease and a medical test used to detect it. Find each
probability.
5) P(D) =
D = the person has the disease
6) P( P I D) =
H = the person is healthy
7) P(D and P) =
P = the person tested positive
8) P(H and P) =
N = the person tested negative
A college computer lab has 100 computers. 70% of the computers are new and 30% of the computers are old. Of
the new computers 20% are Dells and the rest are Macs. Of the old computers 50% are Dells and the rest are Macs.
Find the following.
9) P( the computer is a Dell I it’s new) =
10) P(It’s a Dell and its new) =
11) P(it’s a Mac I it’s old) =
A football team has a 70% chance of winning when it does not snow, but only a 40% chance of winning if it does
snow. Suppose there is a 50% chance that it will snow.
12) Using a tree diagram, find the probability that they will win.
*Bonus: Sixty percent of a company’s sales representatives have completed a training seminar. Of these, 80% have
increased their sales. Overall, 56% of the representatives have increased their sales. Use a tree diagram to find the
probability of increased sales, given that a representative has not been trained.*
A college computer lab has 100 computers. 70% of the computers are new and 30% of the computers are old. Of
the new computers 20% are Dells and the rest are Macs. Of the old computers 50% are Dells and the rest are Macs.
Find the following.
9) P( the computer is a Dell I it’s new) =
10) P(It’s a Dell and its new) =
11) P(it’s a Mac I it’s old) =
A football team has a 70% chance of winning when it does not snow, but only a 40% chance of winning if it does
snow. Suppose there is a 50% chance that it will snow.
12) Using a tree diagram, find the probability that they will win.
*Bonus: Sixty percent of a company’s sales representatives have completed a training seminar. Of these, 80% have
increased their sales. Overall, 56% of the representatives have increased their sales. Use a tree diagram to find the
probability of increased sales, given that a representative has not been trained.*