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Midterm 2.docx

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Simon Fraser University
STAT 100
Thomas Loughin

STAT 100 Midterm 2a Fall 2009 NAME:_______________________ ID:______________________ INSTRUCTIONS: Answer all questions on all pages. Write your answers clearly in the spaces provided. Where computations are required, you should show work. Incorrect answers without clearly-displayed work cannot be considered for partial credit. If a question calls for an explanation, provide one that is complete. Do not omit important details or include irrelevant or incorrect statements. True/False or multiple choice questions need not be accompanied by an explanation. If you have difficulty, or feel like you are working slowly, solve the easiest problems first. Total points on exam: GOOD LUCK! “All of these liars and cheats and thieves are graduates of our universities.'' Robert Gates, President of Texas A & M University, in his inaugural speech referring to recent scholarly, corporate and political corruption. STAT 100 Midterm 1, Fall 2009 QUESTION 1 (8 pts) Insects grow at rates that depend on the temperature: the warmer it is, the faster they grow. Experiments are often run to study how the growth rate of a particular species of insect depends on temperature. Growth rate is defined in terms of how much insects grow in one day. A straight line regression model is used to represent the relationship between temperature and growth rate. One particular experiment was run studying insects raised at different temperatures ranging between 15C-35C. The regression equation was y = -11.2 + 0.95 x. The RMSE was 0.96 and the R was 0.49. A visual inspection of the scatterplot indicated that a straight line was a reasonable model. A. (1 pt) For this regression, what variable would be “x” and what variable would be “y”? B. (1 pt) Explain what -11.2 measures in terms of the insects. C. (1 pt) Explain what 0.95 measures in terms of the insects. D. (1 pt) The average temperature in the summer where these insects live is about 20C. Predict the growth rate at that temperature. a. (1 pt) Within what interval would you expect about 95% of insects’ growth rates to be? E. (1 pt) This species is actually a helpful insect. Another environment where people are considering importing this insect has an average temperature of 10C during the time when these insects could do the most good. Predict the growth rate at that temperature. a. (1 pt) Comment on why this should not be expected to be a reliable prediction. F. (1 pt) What is the correlation between temperature and growth rate? 2 STAT 100 Midterm 1, Fall 2009 QUESTION 2 (4 pts) Political idology vs. gender in US voters, 1991 Male Very Liberal Slightly Liberal Moderate Slightly Conservative Female Very Conservative 0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 The chart above is based on data from a 1991 survey of 832 U.S. voters who identified their own political ideology. Note that the categories in the bars are in the same order as in the legend. A. (1 pt) For each gender,
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