Get out your Residuals Worksheet!
Today’s Objectives:
You will be able to distinguish between
correlation and causation.
Warm Up
Does one cause the other? If so, which
one? If not, explain the situation?
1. Water and plant growth
2. Coffee consumption and nervousness
3. Increase in people exercising and increase
in people committing crimes
4. Money spent on advertising and sales
Homework Check
.44
y=0.18+0.3x
-.42
1.09
-1.02
1.99
.48
.18
.12
-.72
1.39
.78
1.69
-1.32
.42
-2.1
3.02
2.13
-4.5
1.82
.12
1.72
-.39
-.78
1.31
-2.68
3
2.5
2
1.5
1
0.5
0
-0.5
-1
-1.5
-2
-2.5
-3
-3.5
-4
-4.5
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
Homework Check
.78
y=40.26+0.48x
116.65 135.75 207.36 130.97 150.07 102.33 123.81 162.01 140.52 128.59 169.17
3.35
4.25
2.64
29.03
-40.07
12.67 11.19 37.99 -50.52 -3.59
.83
92.78
-7.78
60
50
40
30
20
10
0
-10
-20
30
-40
-50
-60
350
340
330
320
310
300
290
280
270
260
250
240
230
220
210
200
190
180
170
160
150
140
130
120
110
Causation
There is a strong correlation between cigarette
smoking and lung cancer.
Does smoking cigarettes cause lung cancer?
There is strong association between the
availability of hand guns in a nation and that
nation’s homicide rate from guns.
Does easy access to handguns cause more
murders?
Examples from the Book
Get out your book.
Turn to pg. 184
Definitions to notice:
•
•
•
•
Lurking Variable
Common Response
Confounded
Direct cause-and-effect
Possible Relationships
1. Direct cause-and effect
2. Common response
3. Coincidence
Practice
State the relationship among the following variables
as: direct cause-and-effect, common response, or
coincidence. Explain your reasoning.
1. Speed and breaking distance
2. Number of stop signs in a city and the number of
families with 3 children
3. High school grades and college grades
Examples
There is a positive association between ice
cream sales and the number of people who
drown.
Does that mean eating ice cream causes people
to drown?
Compose a more plausible explanation that
involves common response.
Evidence for Causation
The best evidence for causation comes from
well-designed experiments.
What if we cannot do an experiment? How do
we establish causation?
Turn to pg. 187
More Examples
Turn to pg. 188
Individually work through #4.40, 4.41,
and 4.43
Compare your answers with a friend.
QUIETLY!
Quiz Review
Quiz 2 is scheduled for Friday.
It will cover all of Ch. 4.
Key concepts are:
scatterplots, direction strength, correlation, regression line,
slope, y-intercept, residuals, and causation