Introductory Statistics 9th Edition

Published by Wiley
ISBN 10: 1-11905-571-7
ISBN 13: 978-1-11905-571-6

Chapter 4 - Section 4.2 - Calculating Probability - Exercises - Page 140: 4.28


The relative frequency approach to probability is being used.

Work Step by Step

There are two outcomes for a randomly selected family from Los Angeles: "earns more than 175,000 dollars a year" or "earns less than 175,000 dollars a year". These two outcomes are not equally likely. Hence, the experiment is repeated again and again and we will use the relative frequency approach to probability. Suppose a random sample of 1000 families from Los Angeles are selected and observes that 490 of them earn more than 175,000 dollars a year, and 510 of them earn less than that. Then, n = sample size = 1000 f = number of families who earn 175,000 dollars a year = 490 P(a randomly selected family earns more than 175,000) =$\frac{f}{n}$ = $\frac{490}{1000} = 0.49$
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