**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.

**Journal Assignment: **

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: **

On blackboard

**Announcements**

Journals due Tues Sept 29