Practice_questions_for_first_midterm[1]

Practice_questions_for_first_midterm[1] - Midterm#1 March 2...

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Unformatted text preview: Midterm #1 - March 2, 2006 1. Here is a histogram for the distribution of -_.._s.now|evelsininchesforseyeralseasonsat, . ,_ ., ,, a Disincline Valley ski resort: a. Describe the shape of the distribution. b. Approximately how much snow was there in the season with the most snow? c. For this distribution would the mean snow level would be smaller than the median level, bigger than the median, about the same as the median or is it impossible to tell? SNOW finches) 2. A standard deviation contest: Choose 4 numbers from this list: 2, 4, 6, 8, 10, 12, 14, 16 - a. so that the standard deviation is as big as possible b. so that the standard deviation is as small as possible 3.Sketch scatterplots to match the following values of r: r = —.8, r = + .5, r = 1.0 4. Here is data for 5 students on two variables: X = the distance they live from campus, Y = the number of courses they are taking -“flflfl- a. Make a scatterplot for this data. b. Find the regression equation and draw it on your scatterplot To get you started, here are some results: X has mean 8 miles, standard deviation 4 miles. Y has mean 3 classes, standard deviation 1 class. The correlation between X and Y is r = .625. c. Give the regression prediction for the number of classes taken by a student who lives 14 miles from campus. Find the residual (prediction error) for that student. d. Give an interpretation of the slope of the regression line. e. Add an influential observation to your scatterplot. 5. Seal # 3196 is a female elephant seal. Scientists have recorded the depths of her dives when she is feeding in the deep ocean. The dives follow a normal distribution with mean 1370 feet and standard deviation 520 feet. ' a. Sketch the distribution of her dive depths. . b. Fill the blanks: the middle 95% of her dives are between and feet deep. 0. What percent of her dives are more than 1000 feet deep? d. How deep does a dive have to be to be in the 25% of her dives that are the deepest? 6. Here are the lengths of 13 letters to the editor of the Radical Exponent 35, 39, 52, 63, 67, 70,79, 82, 89, 94, 123 a. Make a stemplot for this data. and describe the distribution b. Find the median and quartiles of the distribution. c. On graph paper, make a boxpiot for this data. 7. There is a strong positive association between a person's education level and their lifetime earnings. This could be a case of cause- and- effect. or it could be due to a lurking variable. For each of these situations, explain carefully how it could be the case. 8.-.Al. AbeandAri had the scares pittieirslassmates on thefirstandseeqnd.midterm.exam§.__Eth9ne-a--. .1-.- . A found the correlation, r. betweenthe two sets of scores. a. Al said, “i got a negative value for the correlation. That means that I must have made a mistake, because r can never be negative." is Al right about what his value means? Answer “yes” or “no” and explain briefly. b. Abe said, "l got a positive value of r for the correlation. That means that the class did better on the second midterm than they did on the first.” is Abe right about about what his value means? Answer “yes” or "no" and explain briefly. c. Ari said, “i got r = .95 for my value of r. That means that everyone got just about the same score on the second exam as they had on the first one.” is Ari right about about what his value means? Answer “yes” or "no” and explain briefly. ...
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