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quiz_02_22feb2012_sols

# quiz_02_22feb2012_sols - Name Assigned TF and Section time...

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Name: Assigned TF and Section time: Statistics 100 Quiz 2 Wednesday 22 February 2012 This quiz has four questions and is worth 25 points; two of the questions are on the second page. The scatterplot below shows infant mortality (deaths in the first year of life per 1,000 births) vs number of doctors per 100,000 members of the population for the 50 states plus the District of Columbia. To the right of the plot is part of the Stata output for a least squares regression line fit to the data. 4 6 8 10 12 Inf Mortality 200 400 600 800 Doctors per 100,000 ------------------------------ infmortality | Coef. -----------------+------------ docsper100000 | .0020496 _cons | 6.362203 ------------------------------ 1. The r 2 for these data is 0.0194; what is the correlation coefficient? [Answer] Since the slope of the least squares regression line is positive (0 . 0020496), the correlation coefficient is also positive, and therefore r = r 2 = 0 . 0194 = 0 . 139. 2. Massachusetts has 469 doctors per 100,000 members of the population, and an observed infant mortality 4.8 per 1,000 births. What is the predicted infant mortality for Massachusetts and what is the error of the prediction (the term we called the residual).

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