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Chapter 10: Q. 46 (page 598)

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

Use the following information to answer the next five exercises. A researcher is testing the effects of plant food on plant growth. Nine plants have been given the plant food. Another nine plants have not been given the plant food. The heights of the plants are recorded after eight weeks. The populations have normal distributions. The following table is the result. The researcher thinks the food makes the plants grow taller.

Is the population standard deviation known or unknown?

Use the following information to answer the next five exercises. A study was conducted to test the effectiveness of a software patch in reducing system failures over a six-month period. Results for randomly selected installations are shown in Table 10.21. The “before” value is matched to an “after” value, and the differences are calculated. The differences have a normal distribution. Test at the 1% significance level.

What is the random variable?

Use the following information to answer the next twelve exercises. In the recent Census, three percent of the U.S. population reported being of two or more races. However, the percent varies tremendously from state to state. Suppose that two random surveys are conducted. In the first random survey, out of 1,000 North Dakotans, only nine people reported being of two or more races. In the second random survey, out of 500 Nevadans, 17 people reported being of two or more races. Conduct a hypothesis test to determine if the population percents are the same for the two states or if the percent for Nevada is statistically higher than for North Dakota.

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

The mean number of English courses taken in a two–year time period by male and female college students is believed
to be about the same. An experiment is conducted and data are collected from 29 males and 16 females. The males took an
average of three English courses with a standard deviation of 0.8. The females took an average of four English courses with
a standard deviation of 1.0. Are the means statistically the same?

Use the following information to answer the next five exercises. The mean speeds of fastball pitches from two different baseball pitchers are to be compared. A sample of 14 fastball pitches is measured from each pitcher. The populations have normal distributions. Table 10.18 shows the result. Scouters believe that Rodriguez pitches a speedier fastball.

At the 1 % significance level, what is your conclusion?
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