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quiz10_key - 5 2.4 3.9 5 2.5 3.9 5 3.3 4.1 5 3.3 4.8 5 K 1...

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NAME: Stat 205 Quiz 10 Substances to be tested for cancer-causing potential are often painted on the skin of mice. The question arose whether mice might get an additional dose of the sustance by licking or biting their cagemates. To answer this question, the compound benzo(a)pyrene was applied to the backs of ten mice. n 1 = 5 were individually housed and n 2 = 5 were group housed in a single cage. After two days, the concentration of the compound in the stomach tissue of each mouse was measured. The results (mmol/g) were as follows: Singly housed Group housed 3.3 3.9 2.4 4.1 2.5 4.8 3.3 3.9 2.4 3.4 (a) Compute the Wilcoxin-Mann-Whitney counts K 1 and K 2 . Answer: Sort the data and per- form the counting as shown in class: Less than Singly housed (sorted) Group housed (sorted) Less than 0 2.4 3.4
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Unformatted text preview: 5 2.4 3.9 5 2.5 3.9 5 3.3 4.1 5 3.3 4.8 5 K 1 = 0 K 2 = 25 (b) Check that K 1 + K 2 = n 1 × n 2 . Answer: 0 + 25 = 5 × 5 . (c) Compute the test statistic U s . Answer: U s = 25 , the larger of K 1 or K 2 . (d) Compute the p–value for the test, perhaps by bounding using Table 6 (pp. 680–684). Use a two-sided alternative. Answer: According to Table 6, the p-value is 0.01. It’s ﬁne to say p < . 01 too here. (e) Do you accept or reject that the distributions are the same at the 5% signiﬁcance level? Why? Answer: We reject that the populations of group housed and singly housed mice have the same distribution of benzo(a)pyrene in their stomachs at the 5% level because p < . 01 < . 05 ....
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This note was uploaded on 12/14/2011 for the course STAT 205 taught by Professor Hendrix during the Fall '09 term at South Carolina.

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