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Chapter 9: Q.15 (page 547)
When asked to explain the meaning of the P-value in Exercise 13, a student
says, 鈥淭his means there is only probability 0.01 that the null hypothesis is true.鈥� Explain clearly why the student鈥檚 explanation is wrong.
The student鈥檚 explanation is wrong.
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Fonts and reading ease Does the use of fancy type fonts slow down the reading of text on a computer screen? Adults can read four paragraphs of text in the common Times New Roman font in an average time of seconds. Researchers asked a random sample of adults to read this text in the omate font named Gigi. Here are their times, in seconds:
| 23.2 | 21.2 | 28.9 | 27.7 | 29.1 | 27.3 | 16.1 | 22.6 | 25.6 | 34.2 | 23.9 | 26.8 |
| 20.5 | 34.3 | 21.4 | 32.6 | 26.2 | 34.1 | 31.5 | 24.6 | 23.0 | 28.6 | 24.4 | 28.1 |
Do these data provide good evidence that the mean reading time for Gigi is greater than seconds? Carry out an appropriate test to help you answer this question.
- Use a confidence interval to draw a conclusion for a two-sided test about a population mean.
Refer to Exercise 2. For Yvonne's survey, 96 students in the sample said they rarely or never argue with friends. A significance test yields a P-value of 0.0291.
(a) Interpret this result in context.
(b) Do the data provide convincing evidence against the null hypothesis? Explain.
Anemia For the study of Jordanian children in Exercise , the sample mean hemoglobin level was mg/dl and the sample standard deviation was mg/dl.
(a) Calculate the test statistic.
(b) Find the P-value using Table . Then obtain a
more precise P-value from your calculator.
Reporting cheating What proportion of students
are willing to report cheating by other students? A
student project put this question to an SRS of 172
undergraduates at a large university: 鈥淵ou witness two
students cheating on a quiz. Do you go to the professor?鈥�
The Minitab output below shows the results of a
significance test and a 95% confidence interval based
on the survey data.18
(a) Define the parameter of interest.
(b) Check that the conditions for performing the significance test are met in this case.
(c) Interpret the P-value in context.
(d) Do these data give convincing evidence that the actual population proportion differs from 0.15? Justify your answer with appropriate evidence.
Significance tests A test ofversus Ha : p >0.5 has test statistic z=2.19.
(a) What conclusion would you draw at the 5 % significance level? At the 1 % level?
(b) If the alternative hypothesis were what conclusion would you draw at the 5% significance level? At the 1 % level?
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