Page 128 - Quantitative Data Analysis

Quantitative Data Analysis
Simply Explained Using SPSS

– No extraneous variable causes both A and B.

• Example: A positive
correlation exists between the
amount of ice cream eaten and
crime rate. Does this mean that
eating ice cream causes crime?
A third variable temperature
(confounding variable) causes
to influence both variables (ice
cream sales and crime rate).

For instance, homeless population and crime rate might be
correlated, in that both tend to be high or low in the same locations.
It is equally valid to say that homeless population is correlated with
crime rate, or crime rate is correlated with homeless population. To
say that crime causes homelessness, or homeless populations cause
crime are different statements. And correlation does not imply that
either is true. For instance, the underlying cause could be a 3rd
variable such as drug abuse, or unemployment. Same correlation
can be found between Sunglasses and the Ice Cream Sales but again
the cause for both is the outdoor temperature.

The Theory and Applications of Statistical Inferences 112