Life Expectancy

Lenny calculates a correlation of 0.30. How much of the variation in y is explained by the relationship between x and y?

Alice plots data for many nations of the world. She plots the percentage of people with cell phones on the x axis and the life expectancy in that nation on the y axis. She finds a strong positive correlation between these variables. She decides to embark on a global campaign to provide cell phones for everyone to increase life expectancy especially in poor nations. Is she making any kind of statistics mistake? Explain using terminology

Joe finds the math grades (as a percentage) and history grades (as a percentage) for a group of students. Using x as the math grade and y as the history grade he finds the regression line to be y = 0.53x + 48.5

a. If a student has a 78 percent in math what is there predicted score in history?

b. Jane has 61 percent in math but 83 in history. What is her residual?

c. If a student has 15 percent in history should we use that score to predict their math score? Would that be a problem? Use the wording in the book to explain.

Sally wants to calculate the regression line to use the math grade of a student to predict their chemistry grade? [percentage grades] The correlation coefficient is r = 0.87. The average math grade was 76.5 (with standard deviation 8.1) and the average chemistry grade was 72.3 (with standard deviation 6.7) What is the regression line that uses a math grade to predict a chemistry grade? Show your calculations and explain.

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