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STAT 205 Name: _____ ANSWER KEY_ Spring 2007 Exam 2 P{Y = j} = n C j p j (1 – p) n-j Z = n Y n s t Y 2 t = n s Y 2 2 2 1 2 1 2 2 1 ) ( n s n s t Y Y t = 2 2 2 1 2 1 2 1 0 ) ( n s n s Y Y

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2 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 0.06. Obviously, in this case we fail toreject H 0 . If an error was made, it would be a Type I / Type II / neither error. 3) Suppose you want to analyze a sample of size n=10 and your QQplot shows a violation of normality. In practice, a transformation is commonly attempted before using a non- parametric test. 4) (Circle one) True / False A t -distribution based confidence interval for the mean, , and a t -distribution based hypothesis test for the mean, , are different forms of the same inference. 5) (Circle the correct answer) Twenty institutionalized epileptic patients participated in a study of a new anticonvulsant drug Valproate. Ten of the patients (chosen at random) were started on the daily Valproate and the other ten received an identical placebo pill. During an eight week observation period, the number of major and minor seizures was counted. After this, the patients were “crossed over” to the other treatment, and seizure counts were made during a second eight week observation period. We would use the independent / dependent (paired) samples method in order to conduct a test of hypothesis. 6) We learned several standard error of means (SEMs) for use in making inference on the population mean. In the independent samples setting, we have been applying one type of
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