Exam 3 Review

# Exam 3 Review - a For samples of size 55 what are the mean...

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1. A USA Today/Gallup poll found that out of 1128 randomly chosen adult Americans, 458 supported the direction the government is heading. a. Find a 95% confidence interval for the proportion of all adult Americans who support the direction the government is heading. (8 pts.) b. Interpret the 95% confidence interval. (4 pts.) c. Is the confidence interval valid? Why or why not? (6 pts.) d. What are two ways we can make a narrower confidence interval? (6 pts.) 2. Finding P-values a. Given H a : p ≠ p 0 , what is the P-value if the test statistic is determined to be z = 1.62? (3 pts.) b. Given H a : p > p 0 , what is the P-value if the test statistic is determined to be z = 2.75? (3 pts.) c. Given H a : p < p 0 , what is the P-value if the test statistic is determined to be z = -1.75? (3 pts.)

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3. For students enrolled at a USC the mean and standard deviation for high school grade point average are 3.42 and 0.24, respectively.
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Unformatted text preview: a. For samples of size 55, what are the mean and standard deviation of the sampling distribution of sample means? (4 pts.) b. For a sample of size 55, what is the probability that the sample mean high school grade point average is higher than 3.49? (4 pts.) c. For a sample of size 55, what is the probability that the sample mean high school grade point average is lower than 3.34? (4 pts.) 4. A computer company claims that 60% of college students prefer their line of laptops. A consumer advocacy group believes the claim is wrong and that the true proportion of students preferring that brand of computer is less than 60%. A survey shows that 300 out of 560 randomly chosen dentists prefer that brand of toothpaste. Test the claims using an α = 0.05 level of significance. (25 pts.) Assumptions Hypotheses Test Statistic P-value Conclusions...
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## This note was uploaded on 06/16/2011 for the course STAT 201 taught by Professor Li during the Fall '07 term at South Carolina.

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Exam 3 Review - a For samples of size 55 what are the mean...

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