correlations

• What is a correlation?

  A correlation illustrates the strength and direction of an association between two or more co-variables.
• Positive correlation

  one variable increases and the other also increases

  as one decreases so does the other

  both variables move in the same direction
• Negative correlation

  as one variable increases the other decreases
• Zero correlation

  no relationship between variables
• Difference between a correlation and experiment

  experiment - researcher controls and manipulates the IV in order to measure the effect on the DV.

  correlation - no manipulation of one variable and therefore it is not possible to establish cause and effect between co-variable and another,
• Correlation strengths


  • useful tool for research
  • provide a precise and quantifiable measure of how two variables are related
  • suggest ideas for future research
  • starting point before committing to an experimental study
  • quick and economical to carry out
• Correlation weaknesses


  • cannot explain WHY correlations are related.
  • cannot demonstrate cause and effect between variables.
• Co-variables


  The two factors/variables that are measured/collected by the researcher and then compared to each other.

  Examples: Age, IQ, height or reaction time.
• Scattergram

  A graph used to plot the measurements of two co-variables. Scattergrams visually display the relationship between co-variables.
• Analysis of the relationship between co-variables

  Scattergrams and coefficients indicate the strength of a relationship between two variables, which highlights the extent to which two variables correspond.
• Correlation coefficient

  Represents both the strength and direction of the relationship between the co-variables as a number between -1 and +1.