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Chapter 9: Q.94 (page 592)
Significance and sample size A study with subjects reported a result that was statistically significant at the level. Explain why this result might not be particularly large or important.
The sample size is too much large and for such large samples the value of the test statistic
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Ancient air The composition of the earth鈥檚 atmosphere may have changed over time. To try to discover the nature of the atmosphere long ago, we can examine the gas in bubbles inside ancient amber. Amber is tree resin that has hardened and been trapped in rocks. The gas in bubbles within amber should be a sample of the atmosphere at the time the amber was formed. Measurements on specimens of amber from the late Cretaceous era ( million years ago) give these percents of nitrogen:
Explain why we should not carry out a one-sample t test in this setting.
After checking that conditions are met, you perform a significance test of versus . You obtain a value of . Which of the following is true?
(a) Aconfidence interval for will include the value
(b) A confidence interval forwill include the value .
(c) A confidence interval forwill include the value
(d) A confidence interval for will include the value
(e) None of these is necessarily true.
A college professor suspects that students at his school are getting less than 8 hours of sleep a night, on average. To test his belief, the professor asks a random sample of students, 鈥淗ow much sleep did you get last night?鈥� Here are the data (in hours):
Do these data provide convincing evidence in support of the professor鈥檚 suspicion? Carry out a significance test at the level to help answer this question.
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.
The z statistic for a test of H0 :p = 0.4 versus Ha : p > 0.4 is z = 2.43. This test is
(a) not significant at either or .
(b) significant at but not at
(c) significant at but not at .
(d) significant at both and .
(e) inconclusive because we don鈥檛 know the value of 藛p .
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