Class 8: Correlation
Computer Lab: Correlation
On Blackboard, under Data Sets, there are several Excel files, involving SAT scores and income, meat consumption and height, brain size and IQ, and temperature and crawling age.
We will choose one of them in class to analyze. We will start by making a scatterplot and then we will compute correlation.
Pick a data set of interest to you from Blackboard. (Please donŐt use the class survey data.) Use Excel to complete this assignment.
1) Find two variables that you think may be related. Decide which variable you want to think of as the independent variable and which one you want to think of as the dependent variable.
2) Make a scatterplot of the variables. The independent variable goes on the x-axis. Be sure to label your axes and title your plot. Print out the plot to include in your journal
3) Based on the scatterplot, do the two variables look like they are associated? Does the association look positive or negative, weak or strong?
4) Compute the correlation coefficient using Excel and write it down. Does the number agree with your visual interpretation in part 3?
5) Discuss why the two variables might be related. For example, if you chose the meat consumption and height data, do you think higher per capita meat consumption is causing bigger average height, or vice versa, or neither, and why? What other factors could be behind the relationship between high meat consumption and bigger height? If you chose a different data set, answer the analogous questions about it.
6) Include any other thoughts or comments about what information would be helpful to better decide on how the variables are related.
Homework Assignment 8 for Thurs, Sept. 24:
Journals due Tues Sept 29