SOCY201-10-Correlation.pdf - Correlation Alan Neustadtl...

Correlation
Alan Neustadtl
Department of Sociology
University of Maryland, College Park

Correlation—Basic Concepts
● Correlation is a statistical technique that allows
the exploration of the relationship between two
continuous measures or variables that approx-
imate continuous measures.
● There are several significant characteristics of correlation coefficients or
Pearson’s r :
● Positive Characteristics:
• ranges from -1 to +1 indicating both the direction and degree of the
relationship
• is invariant to changes in the scale of the variables
• controls for sample size
● Negative Characteristics:
• can only detect linear relationships
• is sensitive to extreme cases
• does not determine causality–correlation is a necessary but not
sufficient causal condition

Correlation—Characteristics of Relationships
Type of
Relationship
Characteristics
positive
Large values of X are typically paired with large values
of Y ; average values of X are typically paired with
average values of Y ; and small values of X are typi-
cally paired with small values of Y .
negative
Large values of X are typically paired with small values
of Y ; average values of X are typically paired with
average values of Y ; and small values of X are asso-
ciated with large values of Y .
no linear
relationship
Values of X are randomly paired with values of Y .

Example Correlation Matrix
sexfreq age socbar socrel socommun socfrend
age -0.36
***
socbar 0.20
***
-0.29
***
socrel
-0.08
**
-0.13
***
0.04
socommun 0.03 -0.06
*
0.15
***
0.13
***
socfrend 0.14
***
-0.24
***
0.32
***
0.22
***
0.22
***
mean 53.81 47.97 2.46 4.70 3.50 4.12
sd 66.31 17.68 1.70 1.64 2.06 1.60
N
1,752 2,041 1,426 1,425 1,426 1,425
Source: GSS 2010
*
p <0.05
**
p <0.01
***
p <0.001 (two-tailed tests)
Correlation Coefficient Example
0
20
40
60
80
Sexual Frequency
18-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80-84 85-89
Source: General Social Survey, 2010
Average Yearly Sexual Frequency by Age Group
40
50
60
70
80
Sexual Frequency
ne
v er
on
c
e
a year
sev
ti
m
es a
year
onc
e a month
s
ev
times
a mnth
sev
ti m
es
a
w
eek
al
m
ost dail
y
Source: General Social Survey, 2010
Average Yearly Sexual Frequency by Going to Bars