pracexamquesfall20081

pracexamquesfall20081 - Practice Exam Questions and...

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for Midterm, Fall 2008 Statistics 301, Professor Wardrop 1. Sarah performs a CRD with a dichotomous re- sponse. She obtains the sampling distribution of the test statistic for Fisher’s test for her data; it is given below. x P ( X = x ) P ( X x ) P ( X x ) 0 . 6667 0 . 0001 0 . 0001 1 . 0000 0 . 5278 0 . 0024 0 . 0025 0 . 9999 0 . 3889 0 . 0242 0 . 0267 0 . 9975 0 . 2500 0 . 1104 0 . 1371 0 . 9733 0 . 1111 0 . 2588 0 . 3959 0 . 8629 0 . 0278 0 . 3220 0 . 7179 0 . 6041 0 . 1667 0 . 2094 0 . 9273 0 . 2821 0 . 3056 0 . 0652 0 . 9925 0 . 0727 0 . 4444 0 . 0075 1 . 0000 0 . 0075 (a) Find the P-value for the first alternative ( p 1 > p 2 ) if x = 0 . 1667 . (b) Find the P-value for the second alternative ( p 1 < p 2 ) if x = 0 . 2500 . (c) Find the P-value for the third alternative ( p 1 n = p 2 ) if x = 0 . 1111 . (d) Determine both the P-value and x that sat- isfy the following condition: The data are statistically significant but not highly sta- tistically significant for the second alter- native ( p 1 < p 2 ). (e) Determine all combinations of P-values and x ’s that satisfy the following condi- tion: The data are statistically significant but not highly statistically significant for the third alternative ( p 1 n = p 2 ). (f) Suppose that you want to draw the proba- bility histogram of this sampling distribu- tion. How tall is the rectangle centered at x = 0 . 0278 . 2. A comparative study, with two treatments, di- chotomous response and randomization is per- formed. The study is not balanced. The observed value of the test statistic, x , is a positive number. The exact P-values for all three alternatives are obtained and are below. 0.3329, 0.6211 and 0.8234. Match each P-value with its alternative. Alternative > < n = 3. A comparative study, with two treatments, di- chotomous response and randomization is per- formed. The study is balanced. The observed value of the test statistic, x , is a negative number. The exact P-values for all three alternatives are obtained. The three exact P-values are below along with three other num- bers. Also note that for the actual value of x , P ( X = x ) = 0 . 1257 . 0.0863, 0.1215, 0.4336, 0.6921, 0.8672 and 0.9507, Identify the three P-value and match each with its alternative. Alternative > < n = 4. Consider an unbalanced study with ten subjects, identified as A, B, C, D, E, G, H, J, K and L. In the actual study, Subjects A, B, C and D are assigned to the first treatment, and the other subjects are assigned to the second treatment. There are exactly four successes, obtained by A, E, G and L. This information is needed for parts (a)–(c) be- low. (a) Compute the observed value of the test statistic. 1

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pracexamquesfall20081 - Practice Exam Questions and...

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