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Stat 104 – Homework 3 Due Thursday February 2, 2012 Reading: January 24 – February 2 February 7 – February 14 Chapter 3 Chapter 4 Assignment: 1. Complete the following problems from the text: 3.1, 3.5, 3.11, and 3.16. 2. Public opinion surveys are often conducted over the telephone. Until recently, people conducting surveys contacted only landline telephones because including cell phones in their samples would add significantly to the cost and difficulty of conducting the surveys. Excluding cell phones could bias the results of surveys if characteristics of cell phone users are different from those who have landline telephones. Below is a summary of phone ownership and age for 982 adults in the United States. We wish to see if age can explain some of the variability in phone ownership. Age (years) 18 – 29 30 – 49 50 – 64 65 + Total Landline only 54 200 262 239 755 Cell phone only 94 87 37 9 227 Total 148 287 299 248 982 Phone a) What proportion of the sample has cell phones only? b) Compute row percentages, conditional proportions, for the various age categories for landline and cell phone owners. c) Below is a mosaic plot depicting the percentages calculated in b). Use the percentages from b) and the mosaic plot to compare the age categories in terms of their phone ownership. Your comparison should be written in complete sentences and refer specifically to the percentages and the mosaic plot. Mosaic Plot 1 3. A good bottle of Bordeaux, a red wine from the Bordeaux region of France, can cost a lot of money. Publications, like The Wine Spectator, rate wines with higher ratings indicating better quality wine. We wish to investigate the relationship between the cost of a bottle of Bordeaux and the rating. Below are Price ($) and Rating (on a scale from 0 to 100) for 12 bottles of Bordeaux wine from the 2008 vintage. Price ($) 20 15 11 90 66 50 Rating 89 87 86 91 90 89 Price ($) 40 16 22 43 30 161 Rating 88 88 87 90 89 91 a) Plot the data. Use Price ($) as the explanatory variable, x, and Rating as the response, y. Describe the relationship between Price and Rating. b) Compute the mean and standard deviation for the Price ($). Round final answers to 4 decimal places. c) Compute the mean and standard deviation for the Rating. Round final answers to 4 decimal places. d) Using x x y y 589.0 , compute the correlation between Price ($) and Rating. Round final answer to 4 decimal places. Explain in words what this correlation means. 4. We often read or hear reports about the relationship between diet and health. Data were collected on the fat intake (grams per day per capita) and the death rate (number of deaths per 100,000 people) from colon cancer for 30 nations. The data are available on Blackboard Learn. a) Use Analyze – Distribution in JMP to create graphical displays and numerical summaries of the death rate data. The histogram should be oriented so that death rate is along the horizontal axis. The intervals for death rate should go from 0 to 28 with an increment of 4 and no minor ticks. The histogram should have a vertical axis with a scale and label. Be sure to attach the JMP output to your assignment. Use the JMP output to fully describe the distribution of death rates for the 30 nations. Write your description in complete sentences and be sure to refer specifically to the graphical and numerical summaries. 2