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Chapter 10: Q. 48 (page 598)

Comparing Two Independent Population Proportions.

Use the following information for the next five exercises. Two types of phone operating system are being tested to determine if there is a difference in the proportions of system failures (crashes). Fifteen out of a random sample of 150 phones with OS1 had system failures within the first eight hours of operation. Nine out of another random sample of 150 phones with OS2 had system failures within the first eight hours of operation. OS2 is believed to be more stable (have fewer crashes) than OS1.

State the null and alternative hypotheses

Short Answer

Expert verified

The null and alternative hypotheses is

H0:pos1=pos2H1:pos1>pos2

Step by step solution

01

Given Information

The proportions of system failures for two types of phone operating systems are being compared to see if there is a difference (crashes). Within the first eight hours of operation, fifteen of a random sample of 150 phones with OS1 had system problems. Within the first eight hours of operation, nine out of 150 OS2 phones encountered system problems. OS2 is thought to be more stable than OS1 (it has less crashes).

02

Determine the  null and alternative hypotheses 

The null hypothesis states that the proportion of phones with OS1 or OS2 crashes is the same. The alternative hypothesis is that phones running OS2 are more stable than phones running OS1.

By providing null and alternative hypotheses,

H0:pos1=pos2H1:pos1>pos2

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Most popular questions from this chapter

Use the following information to answer the next 15 exercises: Indicate if the hypothesis test is for

a. independent group means, population standard deviations, and/or variances known

b. independent group means, population standard deviations, and/or variances unknown

c. matched or paired samples

d. single mean

e. two proportions

f. single proportion

Varsity athletes practice five times a week, on average.

A study was conducted to investigate how effective a new diet was in lowering cholesterol. Results for the

randomly selected subjects are shown in the table. The differences have a normal distribution. Are the subjects鈥�

cholesterol levels lower on average after the diet? Test at the 5%level.

SubjectABCDEFGHI
Before209210205198216217238240222
After199207189209217202211223201

Use the following information to answer the next five exercises. A doctor wants to know if a blood pressure medication is effective. Six subjects have their blood pressures recorded. After twelve weeks on the medication, the same six subjects have their blood pressure recorded again. For this test, only systolic pressure is of concern. Test at the 1%significance level.

What is the sample mean difference?

97. A baseball fan wanted to know if there is a difference between the number of games played in a World Series when the American League won the series versus when the National League won the series. From 1922 to 2012 , the population standard deviation of games won by the American League was 1.14, and the population standard deviation of games won by the National League was 1.11. Of 19 randomly selected World Series games won by the American League, the mean number of games won was 5.76. The mean number of 17 randomly selected games won by the National League was 5.42. Conduct a hypothesis test.

Use the following information to answer the next 12 exercises: The U.S. Center for Disease Control reports that the mean life expectancy was 47.6 years for whites born in 1900 and 33.0 years for nonwhites. Suppose that you randomly survey death records for people born in 1900 in a certain county. Of the 124 whites, the mean life span was 45.3 years with a standard deviation of 12.7 years. Of the 82 nonwhites, the mean life span was 34.1 years with a standard deviation of 15.6 years. Conduct a hypothesis test to see if the mean life spans in the county were the same for whites and nonwhites.

State the null and alternative hypotheses.

a. H0:

b. Ha :
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