Chapt7Examples - is which? 4. A survey was conducted in the...

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Chapter 7 Examples 1. Suppose you were to collect data for each pair of variables. You want to make a scatterplot. Which variable would you use as the explanatory variable (predictor) and which as the response variable? Why? What would you expect to see in the scatter plot? Discuss the likely direction, form and strength. a) Long-distance calls: time (minutes), cost b) Lightening strikes: distance from lightning, time delay of the thunder c) A streetlight: its apparent brightness, your distance from it d) Cars: weight of car, age of owner 2. Which of the scatterplots show a) little or no association? b) a negative association? c) a linear association? d) a moderately strong association? e) a very strong association? 3. Here are several scatterplots. The calculated correlations are -0.977, -0.021,0.736 and 0.951. Which
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Unformatted text preview: is which? 4. A survey was conducted in the US and 10 countries of Western Europe to determine the percentage of teenagers who had used marijuana and other drugs. The results are summarized in the table: Percent Who Have Used a) Create a scatterplot of the data. Country Czech Rep. Denmark England Finland Ireland Italy No. Ireland Norway Portugal Scotland USA b) What is the correlation between the percent of teens who have used marijuana and the percent who have used other drugs? c) Write a brief description of the association Marijuana 2 2 17 40 5 37 19 23 6 7 5 3 34 d) Do these results confirm that marijuana is a "gateway drug", that is, that marijuana use leads to the use of other drugs? Explain. Other Drugs 4 3 21 1 16 8 14 3 3 31 2 4...
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This note was uploaded on 04/12/2011 for the course STA 215 taught by Professor Tba during the Spring '08 term at Grand Valley State University.

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Chapt7Examples - is which? 4. A survey was conducted in the...

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