## Elementary Statistics (12th Edition)

Published by Pearson

# Chapter 4 - Probability - 4-5 Multiplication Rule: Complements and Conditional Probability - Basic Skills and Concepts - Page 173: 22

#### Answer

a)0.905 b)0.993 c)They are not equal.

#### Work Step by Step

a)We know that $probability=\frac{number \ of \ good \ outcomes}{number\ of\ all\ outcomes}$, hence $P(Negative|No \ drugs)=\frac{860}{860+90}=0.905.$ b)We know that $probability=\frac{number \ of \ good \ outcomes}{number\ of\ all\ outcomes}$, hence $P(No \ drugs|Negative)=\frac{860}{860+6}=0.993.$ c)$0.905\ne 0.993$, they are not equal.

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