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Chapter 9: Q. 61. (page 584)
The standardized test statistic for a test of versus isThis test is
a. not significant at either or
b. significant at but not at
c. significant atbut not at
d. significant at both and
e. inconclusive because we don鈥檛 know the value of
The test is significant at and
The correct option is
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Significance tests A test of against
based on a sample of size yields the standardized test statistic .
a. Find and interpret the -value.
b. What conclusion would you make at the significance level? Would
your conclusion change if you used instead? Explain your reasoning.
c. Determine the value of = the sample proportion of successes.
Don't argue Refer to Exercise 2. Yvonne finds that of the students say they rarely or never argue with friends. A significance test yields a -value of Interpret the -value.
You are testing against based on an SRS of
observations from a Normal population. What values of the t statistic are statistically significant at the level?
Clean water The Environmental Protection Agency (EPA) has determined that safe
drinking water should contain at most mg/liter of copper, on average. A water supply company is testing water from a new source and collects water in small bottles at each ofrandomly selected locations. The company performs a test at the 伪=0.05 significance level ofversus , where 渭 is the
true mean copper content of the water from the new source.
a. Describe a Type I error and a Type II error in this setting.
b. Which type of error is more serious in this case? Justify your answer.
c. Based on your answer to part (b), do you agree with the company鈥檚 choice of ? Why or why not?
Losing weight A Gallup poll found that 59% of the people in its sample said 鈥淵es鈥� when asked, 鈥淲ould you like to lose weight?鈥� Gallup announced: 鈥淔or results based on the total sample of national adults, one can say with 95% confidence that the margin of (sampling) error is 卤3 percentage points.鈥�12 Based on the confidence interval, is there convincing evidence that the true proportion of U.S. adults who would say they want to lose weight differs from 0.55? Explain your reasoning
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