Download MATH 1070-070: Quiz 4 June 12, 2008 Name: 1

MATH 1070-070: Quiz 4
June 12, 2008
Name:
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1. A man claims to be extremely unlucky. To test this, we flip a fair coin and ask him to guess. Of 50
flips, he guessed 20 correctly. Is he unlucky? Go through the 5 steps for a hypothesis test to test this.
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2. Time magazine quoted a poll of 10,000 Americans in which only 4% said they were vegetarians.
(a) What has to be assumed about this sample in order to construct a confidence interval for the
population proportion of vegetarians.
(b) Construct a 99% confidence interval for the population proportion. Explain why the interval is so
narrow, even though the confidence level is high.
(c) In interpreting this confidence interval, can you conclude that fewer than 10% of Americans are
vegetarians? Explain your reasoning.
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3. In 1999, the American Psychological Association conducted a survey of a random sample of psychologists to estimate mean incomes for psychologists of various types. Of the 10 clinical psychologists
with 5-9 years of experience who were in a medical psychological group practice, the mean income was
$78,5000 with a standard deviation of $33,287.
(a) Construct a 95% confidence interval for the population mean. Interpret.
(b) What assumption about the population distribution of psychologists’ incomes does the confidence
interval method make?
(c) If the assumption about the shape of the population distribution is not valid, does this invalidate
the results? Explain.
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