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STAT 205 Exam 2 Name ______ANSWER KEY ________ Fall 2006 PሼYൌjሽൌ C j p j ሺ1‐pሻ n‐j n Z ൌ Y ‐µ σ √n Y േt α 2 s √n ݐ Y ‐µ s n ሺY 1 ‐Y 2 ሻേ t α 2 s 1 2 n 1 s 2 2 n 2 t Y 1 ‐Y 2 ‐ 0 s 1 2 n 1 s 2 2 n 2

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Part I: Answer eight of the following nine questions. If you complete more than eight, I will grade only the first eight. Five points each. 1) State the definition of a P-value. The probability under H 0 of observing a test statistic as extreme or more extreme (in the direction of H A ) as that actually observed. 2) (Circle the correct answer) A hypothesis test has been conducted at the 0.05 significance level, resulting in a P-value of 0.003. Obviously, in this case, we reject H 0 . If an error was made, it would be a Type I / Type II / neither error. 3) (Circle the correct answer) Suppose you have calculated a 95% confidence interval for the mean, μ . Now, you want to calculate a 99% confidence interval using the same sample. The 99% confidence interval will be narrower / wider than the 95% confidence interval. 4) Consider taking a random sample of size 4 from a population of persons who smoke and recording how many of them, if any, have lung cancer. Let p represent the proportion of persons in the sample with lung cancer. List the possible values of p . 0, 0.25, 0.5, 0.75, 1 5) (Circle the correct answer) Trichotillomania is a psychiatric illness that causes its victims to have an irresistible compulsion to pull their own hair. Two drugs were compared as treatments for trichotillomania in a study involving 13 women. Each woman
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