Fall 2008 Exam 1 - questions and answers

Fall 2008 Exam 1 - questions and answers - Stat 252 Exam 1...

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Stat 252 Exam 1 Rein Fall 2008 1) Identify each statement about independent samples T-tests and CIs as True or False. a. The higher the confidence level, the higher the margin of error. b. The higher the sample sizes, the higher the margin of error. c. The higher the standard deviations, the higher the margin of error. d. If a Confidence Interval for ߤ െߤ includes zero and if ݔҧ is larger than ݔҧ , a null hypothesis of equality would be rejected in favor of an alternative hypothesis of inequality. e. If a Confidence Interval for ߤ includes zero and if ݔҧ is larger than ݔҧ , a null hypothesis of equality would be rejected in favor of an alternative hypothesis that ߤ is larger than ߤ . f. If a Confidence Interval for the difference of means is 2.1±1.1, it should be interpreted in plain English as “We are 95% sure that ݔҧ െݔҧ is in the 1.0 to 3.2 range.” g. If a Confidence Interval for the difference of means is 2.1±1.1, doubling the sample size for each group would cut the margin of error approximately in half. 1a True 1b False 1c True 1d False 1e False 1f False 1g False
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Stat 252 Exam 1 Rein Fall 2008 2) To study the possibility of the housing market crash starting as early as 2005, data on single-family homes in Oakland that sold in both 2006 and 2005 were collected and summary statistics from Minitab are presented: Descriptive Statistics: 2005 Price ($1000s), 2006 Price ($1000s), Difference Variable N Mean StDev 2005 Price ($1000s) 18 477.9 66.2 2006 Price ($1000s) 18 447.0 46.9 Difference 18 30.9 24.1 a. Develop an appropriate 95% Confidence interval for the mean change in price in Oakland between 2005 and 2006 based on these data. For paired data like these, the equation for a 95% Confidence Interval is ݀ ҧ േݐ ఈ/ଶ ඥ௡ . For these data, the CI would thus be ݀ ҧ ఈ/ଶ ඥ௡ ൌ 30.9 േ 2.1098
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This note was uploaded on 10/28/2008 for the course STAT 252 taught by Professor Staff during the Spring '05 term at Cal Poly.

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Fall 2008 Exam 1 - questions and answers - Stat 252 Exam 1...

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