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Chapter 10: Q. 67 (page 599)

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 conclusion can you draw about the software patch?

Short Answer

Expert verified

Reject the null hypothesis with p - value of 0.0067.

There is enough data to show that installing a software patch lowers system failures.

Step by step solution

01

Given information

The table is

02

Step 2: 

Test at 1%level of significance, that is,α=0.01

The output from Exercise 10.49 is :

Asα>p-value, need not reject the null hypothesis.

At 1%level of significance, there is sufficient evidence to back up the assertion that the software patch reduces the number of system failures.

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Most popular questions from this chapter

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. 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.

What is the p-value?

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 OS1had system failures within the first eight hours of operation. Nine out of another random sample of 150 phones with OS2had system failures within the first eight hours of operation. OS2is believed to be more stable (have fewer crashes) than OS1.

What can you conclude about the two operating systems?

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.

Draw the graph of the p-value.

A new laundry detergent is tested on consumers. Of interest is the proportion of consumers who prefer the new brand

over the leading competitor. A study is done to test this.

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
See all solutions

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