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Unformatted text preview: Stat 135, Fall 2006 HOMEWORK 10 (due Friday 12/1) In what follows, you will have to do lots of regressions and pick one or two that are better than the others. DO NOT turn in all the regression output. The only computer output I want to see are the relevant plots, along with a clear discussion of what they imply. The rest of each answer should consist of a carefully written paragraph, including numerical values from your computer work as appropriate. You will have to work out whats appropriate. 1. The dataset chicks was obtained from BLSS: The Berkeley Interactive Statitstical System by Abrahams and Rizzardi. Each observation corresponds to an egg (and the re- sulting chick) of a bird called the Snowy Plover. The data were taken at Point Reyes Bird Observatory. Column 1 contains the egg length in millimeters, Column 2 the egg breadth in millimeters, Column 3 the egg weight in grams, and Column 4 the chick weight in grams. The object is to estimate the size of the chick based on dimensions of the egg. a) First you are going to regress chick weight on egg length. Write out the usual re- gression model in terms of these two variables. Plot the data and comment on whether the assumptions of the model are reasonable. Find the means and SDs of both variables, as well as the correlation between them. Use the formulas you derived in HW 9 to find the slope and the intercept of the regression line. Provide units for the slope and the intercept, and write the equation of the regression line. Draw the regression line on your plot. b) Now use R to regress chick weight on egg length. Check that R produces the same slope and intercept that you got in a . For each of the t and F statitics in the R output, state the null and alternative hypotheses that are being tested, and state the conclusion of the test....
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