1. Correlation and Causation
Part I – Scatterplots 1

2. This video is designed to accompany pages 19-24 in
Making Sense of Uncertainty
Activities for Teaching Statistical Reasoning
Van-Griner Publishing Company 2

3. Vernacular cor·re·la·tion [ kàwrə láysh'n ]
mutual or complementary relationship: a relationship in which two or more things are mutual or complementary
relatedness of variables: the degree to which two or more variables are related and change together 3

4. Example Variables: Height and Weight
Bigger values of Height tend to be associated with bigger values of Weight. 4

5. Scatterplot
A scatterplot of height (y-axis) versus weight (x-axis) would likely look something like this. 5

6. Life Expectancy at Birth
Other Scatterplots
Plots! Oh No!
Time Spent Studying
Student Grades
Hours Exercised
LDL Levels
GNP per capita
Life Expectancy at Birth
Quiz Average
Final Exam Score 6

7. Language of Association
positive association - points have an upward trend from left to right
negative association - points have a downward trend from left to right
strength - points are tightly clustered about some clear pattern (maybe straight line)
Often the word “correlation” is used interchangeably with “association.” That’s OK until we get more technical. 7

8. Life Expectancy at Birth
Scatterplots Revisited
Plots! Oh Yeah!
Time Spent Studying
Student Grades
Hours Exercised
LDL Levels
Negative
Pretty Strong
Moderately Strong
Positive
GNP per capita
Life Expectancy at Birth
Quiz Average
Final Exam Score
Positive
Arguably Pretty Strong
Not Straight Line
Not Very Strong 8

9. Using Your Eyes Scatterplots
Visual way of assessing association, both direction and strength.
Makes sense as long as you have two variables that you can display in a scatterplot 9

10. Association Between Gender and Hours Spent Doing Homework
What do you see? 10

11. One-Sentence Reflection
Simple scatterplots are an informal, but useful visual means of addressing both the direction and strength of the relationship between two variables that are appropriate for this kind of plot.