Correlations

• Correlation


  A statistical measure that indicates the extent to which two or more variables fluctuate together
• Correlational study


  • Researcher does not manipulate any variables, they just measure
  • Has two co-variables that the researcher has measured and then compares
• Displaying a correlation


  1. Plot data on a scattergram

  2. Determine if the correlation is positive, negative or zero
• Correlation coefficient


  A number that describes the strength and direction of the relationship between two variables, ranging from -1 (perfect negative correlation) to +1 (perfect positive correlation)
• Correlation does not show causation
• Increase in one co-variable

  May be due to an increase in the other co-variable, or due to an unknown third variable
• Example of spurious correlation

  • Positive correlation between ice cream sales and death by drowning, due to the third variable of temperature
• Advantages of correlational research

  • Can highlight potential causal relationships for further investigation
  • Often has few ethical problems as it measures pre-existing variables
• Correlation coefficient is a useful tool in describing the strength of a correlation