Table : TABLE 1.5Quiz on Correlation
Two VariablesPositive, Negative, or Zero Correlation?Why? (Third Variable)
  • Ice cream sales and murder rate
    		• __________________________
  • Learning to read and number of baby teeth
    		• __________________________
  • Child gender and sex of parent
    		• __________________________
    For each of these three pairs of variables, indicate whether the correlation between them is positive, negative, or nonexistent. Then try to think of a third variable that would determine the direction of the correlation.
    Answers:
  • Positive; third variable: heat
  • Negative; third variable: age
  • Zero; each child must have a parent of each sex; no third variable.