Multivariate Relationships

1
Multivariate Relationships

• Goal Show a causal relationship between two
  variables (X ? Y)
• Elements of a cause-and-effect relationship
• Association between variables (based on methods
  weve covered this semester)
• Correct time order (X occurs before Y)
• Elimination of alternative explanations (variable
  Z that acts on both X and Y, making them appear
  to be associated)
• Anecdotal evidence does not rule out causality

2
Controlling for Other Variables

• Observational studies Researchers are unable to
  control levels of variables and may only observe
  them as they occur in nature
• Statistical Control Identifying individuals
  (cases) by their level of an alternative
  explanatory (control) variable (although not
  assigning subjects the levels)
• Spurious Association When both variables of
  interest are dependent on a third variable, and
  their association vanishes when controlling for
  the other variable

X1
X2
Y