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solutions_of_samplemidterm1

solutions_of_samplemidterm1 - Stat 155.8 Midterm 1...

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Stat 155.8 Midterm 1 Wednesday, February 16, 2005 Name (please print): INSTRUCTIONS: 1. Answer all questions and show all work on the exam in the space provided. Please be free to use the back pages if necessary. You will not receive credit if you do not justify your answers. 2. Circle your final answers. 3. Remember to sign the Honor Pledge below. I pledge that I have neither given nor received unauthorized assistance during this examination. Signed: ----------------------------------------------------------------------
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1. (8 points) Suppose we are interested in the relationship between height and weight. To examine this relationship, we take a sample of 100 people and measure both the height and weight of each (I.e. for each person, we end up with a pair of numbers (x, y), where x is the height in inches and y is the weight in kilograms .). For this relationship, write down the units of: a) the correlation r between height and weight. r is unitless b) a and b where bx a y + = ˆ is the regression line of weight on height. unit of a: inches unit of b: kg/inches c) X , the mean height. inches d) S x 2 , the variance of the variable height. inches 2 2. (13 points) The following is the stemplot of the salaries (in thousand of dollars) of 15 employees in a company. 8 7 6 5 4 3 2 1 3 1 2 6 1 4 1 7 2 3 8 9 3 5 8 a) Find the five number summary of the distribution. (Min, Q1, M, Q3, Max) = (11, 49, 63, 73, 87) b) Find the mean of the distribution. Mean = 60.2
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c) Is the distribution symmetric/ skewed left /skewed right? d) What kind of measure is a good choice of center in this case? median e) Find the IQR (Inter Quartile Range). Then use the 1.5 x IQR criterion to check for suspected outliers.
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