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Chapter 10: Q.76 (page 600)
What is the sample mean difference?
The mean of differences is
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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.
What is the random variable?
In a random sample of 100 forests in the United States, 56 were coniferous or contained conifers. In a random sample of 80 forests in Mexico, 40 were coniferous or contained conifers. Is the proportion of conifers in the United States statistically more than the proportion of conifers in Mexico?
A concerned group of citizens wanted to know if the proportion of forcible rapes in Texas was different in
than in Their research showed that of the violent crimes in Texas in of them were forcible rapes. In of the violent crimes were in the forcible rape category. Test at a significance level.
Answer the following questions:
a. Is this a test of two means or two proportions?
b. Which distribution do you use to perform the test?
c. What is the random variable?
d. What are the null and alternative hypothesis? Write the null and alternative hypothesis in symbols.
e. Is this test right-, left-, or two-tailed?
f. What is the p-value?
g. Do you reject or not reject the null hypothesis?
h. At the ___ level of significance, from the sample data, there ______ (is/is not) sufficient evidence to conclude that
____________.
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 had system failures within the first eight hours of operation. Nine out of another random sample of 150 phones with had system failures within the first eight hours of operation. is believed to be more stable (have fewer crashes) than .
What can you conclude about the two operating systems?
Use the following information to answer the next 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
According to a television commercial, of dentists agree that Ultrafresh toothpaste is the best on the market
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