homework6

# homework6 - response for each level of the factor 5 Carry...

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Statistics 5021 – Homework 6 There are 20 total points. This homework is due Thursday, April 7 in your lab section. In this homework, you will analyze a dataset (preferably using R ). The data are from an experiment where 24 animals were assigned to one of four diets and then blood coagulation times were measured for each animal. These data are available for download on Moodle in the ﬁle “blood.txt”. 1. In the dataset, the response is called coag and the factor is called diet , with four levels. Produce numerical summaries of the data of your choosing. How many subjects had diet level D? 2. Produce side-by-side boxplots of the response for each level of the factor. 3. Produce a stripchart of the response for each level of the factor. When constructing this plot, use the additional argument: method="stack" . Does there seem to be any strong visual evidence that it is unreasonable to assume the 4 subpopulation distributions of the response have the same standard deviation σ ? 4. Report the observed sample mean and observed sample standard deviation of the
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Unformatted text preview: response for each level of the factor. 5. Carry out the hypothesis test where the null hypothesis is that all subpopulation mean blood coagulation times are equal versus the alternative that at least one is diﬀerent at the 5% signiﬁcance level. (a) What assumptions must be made. State H and H a . (b) Specify the test statistic realization and p-value. (c) What is the distribution of the test statistic when H is true. State the values for its parameters. (d) State the conclusion to this test. Based on this conclusion, what type of error could you be making? (e) Report Tukey HSD simultaneous 95% conﬁdence intervals for the pairwise diﬀer-ences between the subpopulation means of blood coagulation times. Interpret this set of intervals and mention which pairs of subpopulation means are statistically signiﬁcantly diﬀerent at the simultaneous 5% signiﬁcance level. 1...
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## This note was uploaded on 05/06/2011 for the course STAT 5021 taught by Professor Staff during the Spring '08 term at Minnesota.

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