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Comparing Two Independent Population Proportions.

Use the following informotion 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.

Is this a test of means or proportions?

Short Answer

Expert verified

This is a proportions test.

Step by step solution

01

Given Information

Two different phone operating systems are being compared to see if the proportions of system breakdowns change (crashes). Within the first eight hours of operation, fifteen of a random sample of 150 phones with OS1 encountered system failures. Another random sample of 150 phones yielded nine Within the first eight hours of operation, OS2 experienced system difficulties. OS2 is thought to be more stable than OS1 (with fewer crashes).

02

Determine the, is this a test of means or proportions?

The test is determining the percentage of phones with OS1 and OS2 that fail within the first 8 hours of operation.

This is a proportions test.

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Most popular questions from this chapter

A student at a four-year college claims that mean enrollment at four–year colleges is higher than at two–year colleges in the United States. Two surveys are conducted. Of the \(35\) two–year colleges surveyed, the mean enrollment was \(5,068\) with a standard deviation of \(4,777\). Of the \(35\) four-year colleges surveyed, the mean enrollment was \(5,466\) with a standard deviation of \(8,191\).

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

A new WiFi range booster is being offered to consumers. A researcher tests the native range of 12 different routers under the same conditions. The ranges are recorded. Then the researcher uses the new WiFi range booster and records the new ranges. Does the new WiFi range booster do a better job?

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.

Which distribution (normal or Student's t) would you use for this hypothesis test?

Use the following information to answer the next five exercises. Two metal alloys are being considered as material for ball bearings. The mean melting point of the two alloys is to be compared. 15 pieces of each metal are being tested. Both populations have normal distributions. The following table is the result. It is believed that Alloy Zeta has a different melting point.

What is the p-value?

Adults aged 18 years old and older were randomly selected for a survey on obesity. Adults are considered obese if their body mass index (BMI) is at least 30. The researchers wanted to determine if the proportion of women who are obese in the south is less than the proportion of southern men who are obese. The results are shown in Table 10.27. Test at the 1% level of significance.


Number who are obeseSample size
Men42769155,525
Women67169248,775
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