11. Correlation

"In studies of monozygotic (identical) twins, the correlation between intelligence (IQ) scores is 0.85.

c. What fraction of the variation in one twin’s IQ can be accounted for by the other twin’s IQ?"

Why don’t we conduct inference on the linear correlation coefficient?

[DATA] Graduation Rates PayScale reports statistics on colleges and universities. Go to www.pearsonhighered.com/sullivanstats to obtain the data file 11_3_24 using the file format of your choice for the version of the text you are using. The data contain the four-year cost and graduation rate for over 1300 colleges and universities. Do schools that charge more have higher graduation rates? The variable “4 Year Cost” represents the four-year cost of attending the college or university. The variable “Grad Rate” represents the percentage of incoming freshman who graduate within six years.

b. Determine the correlation coefficient between “4 Year Cost” and “Grad Rate.”

[DATA] Putting It Together: Exam Scores The data below represent scores earned by students in Sullivan’s Elementary Algebra course for Chapter 2 (Linear Equations and Inequalities in One Variable) and Chapter 3 (Linear Equations and Inequalities in Two Variables). Completely summarize the relation between Chapter 2 and Chapter 3 exam scores, treating Chapter 2 exam scores as the explanatory variable. Write a report detailing the results of the analysis including the presence of any outliers or influential points. What does the relationship say about the role Chapter 2 plays in a student’s understanding of Chapter 3?