Practice Quiz - Section 7-3 (Form B) - Conditional Probability and Independence

Multiple-choice exercise

Work out the problem on paper and then choose the letter for your answer. After you have successfully answered all questions, look at the top of the page to see how you did.

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A study has been done to determine whether or not a certain drug leads to an improvement in symptoms for patients with a particular medical condition. The results are shown in the following table.

Improvement

No Improvement

Total

Drug

320

480

800

No Drug

160

240

400

Total

480

720

1200

Based on this table, what is the (empirical) probability that a person shows improvement if it is known that the person was given the drug?

.4

.267

.667

None of the answers given; click to see the solution.

The results of the study in question #1 on the relationship between a certain drug and the improvement in symptoms for patients with a particular medical conditon are repeated below.

Improvement

No Improvement

Total

Drug

320

480

800

No Drug

160

240

400

Total

480

720

1200

Suppose it is known that the patient's symptoms improve. Based on this table, what is the (empirical) probability that that the patient was given the drug?

.667

.267

.4

None of the answers given; click to see the solution.

Two cards are drawn in succession from a standard 52-card deck. What is the probability that both cards are face cards if the cards are drawn without replacement?

.0498

.0385

.0533

None of the answers given; click to see the solution.

A box contains five red, two white, and three green marbles, all of which are the same size. Two marbles are selected one after the other from the box, without replacement. What is the probability that the marbles are the same color?

.31

.6

.011

None of the answers given; click to see the solution.

A company has three plants at which it produces a certain item. 20% are produced at Plant A, 30% at Plant B, and 50% at Plant C. Suppose that 1%, 2% and 3% of the items produced at Plants A, B and C respectively are defective. If an item is selected at random from all those produced, what is the probability that the item was produced at Plant B and is defective?

.006

.06

.02

None of the answers given; click to see the solution.

A company has three plants at which it produces a certain item. 20% are produced at Plant A, 30% at Plant B, and 50% at Plant C. Suppose that 1%, 2% and 3% of the items produced at Plants A, B and C respectively are defective. If an item is selected at random from all those produced, what is the probability that the item is defective?

.023

.06

.02

None of the answers given; click to see the solution.

The results of the study in question #1 on the relationship between a certain drug and the improvement in symptoms for patients with a particular medical conditon are repeated below.

Improvement

No Improvement

Total

Drug

320

480

800

No Drug

160

240

400

Total

480

720

1200

Based on this table, are the events "has the drug" and "improvement" independent events?