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This week, we are looking at the relationship between quantitative variables. We will concentrate on two variables for the purpose of this Discussion. We will be looking at the direction—positive or negative—and the strength—weak, moderate, or strong—of the correlation. There are no hard and fast rules on what numbers mean weak, moderate, or strong correlations; however, here is a rule of thumb:

0 < 0.4 weak
0.4 < 0.6 moderate
0.6 – 1 strong, where the numbers can be positive or negative.

Remember that you can only “prove” that one variable “causes” another by using an experiment. Be skeptical of observational studies that claim causation.

To prepare for this Discussion:

  • Review the following resources:

Discussion Resources (click to expand/reduce)

Discussion Videos

Finding Correlation Using Statdisk (4m)

Statdisk to Find r (2m)

StatCrunch: Creating Scatterplots (5m)

Discussion Documents

Scatterplots (PDF)

Correlation (PDF)

  • Look at the data set that you used in Discussion 1 and/or 2. In order to do this week’s Discussion, you will need to have two quantitative variables that you think might be related. In other words, changes in one variable result in changes in the other variable.  If you do not have two variables like this in your data set, add another variable. 

Example: (click to expand/reduce)

  • Review the rubric that will be used for grading.  

With these thoughts in mind:

By Day 1

By the end of Day 1, you can post your scenario and data for your Instructor to review.  If you don’t submit this by the end of Day 1, you will need to proceed to submit the entire Discussion on Day 3.

By Day 3

Post a 1- to 2-paragraph write-up that includes the following: