A survey was conducted in the United States 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 following table. Country Czech Rep. Denmark England Finland Ireland Italy No. Ireland Norway Portugal Scotland United States Percent Who Have Used Other Drugs 4 3 Marijuana 22 17 40 5 37 19 23 6 7 53 34 21 1 16 8 14 3 3 31 24 i) Create a scatterplot, by hand. ii) Write a brief description of the association seen from the scatterplot. iii) Calculate the mean percent of teens who have used marijuana and the mean percent who have used other drugs?

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A survey was conducted in the United States 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 following table.

A survey was conducted in the United States 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
following table.
Country
Czech Rep.
Denmark
England
Finland
Ireland
Italy
No. Ireland
Norway
Portugal
Scotland
United States
Percent Who Have Used
Other Drugs
Marijuana
22
17
40
5
37
19
23
6
7
53
34
4
3
21
1
16
8
14
3
3
31
24
i) Create a scatterplot, by hand.
ii) Write a brief description of the association seen from the scatterplot.
iii) Calculate the mean percent of teens who have used marijuana and the mean percent who have
used other drugs?
iv) Can you spot a country which contributes negatively to the association? If yes, explain how.
v) The standard deviation of the percent of teens who have used marijuana is 15.55% and it is
10.24% for the percent who have used other drugs. Calculate the correlation between the percent
of teens who have used marijuana and the percent who have used other drugs. Show the "by
hand" formula you may use.
vi) What does the correlation coefficient confirm or specify?
vii) Do these results allow you to say that marijuana is a "gateway drug”, that is, that marijuana use
leads to the use of other drugs? Explain.
Transcribed Image Text:A survey was conducted in the United States 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 following table. Country Czech Rep. Denmark England Finland Ireland Italy No. Ireland Norway Portugal Scotland United States Percent Who Have Used Other Drugs Marijuana 22 17 40 5 37 19 23 6 7 53 34 4 3 21 1 16 8 14 3 3 31 24 i) Create a scatterplot, by hand. ii) Write a brief description of the association seen from the scatterplot. iii) Calculate the mean percent of teens who have used marijuana and the mean percent who have used other drugs? iv) Can you spot a country which contributes negatively to the association? If yes, explain how. v) The standard deviation of the percent of teens who have used marijuana is 15.55% and it is 10.24% for the percent who have used other drugs. Calculate the correlation between the percent of teens who have used marijuana and the percent who have used other drugs. Show the "by hand" formula you may use. vi) What does the correlation coefficient confirm or specify? vii) Do these results allow you to say that marijuana is a "gateway drug”, that is, that marijuana use leads to the use of other drugs? Explain.
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