Correlations

• What is a correlation?

  A relationship between two variables (not cause and effect)
• What is a positive correlation?

  A relationship between variables where one increases, the other increases, or as one decreases, the other decreases
• What is a negative correlation?

  A relationship between variables where as one variable increases the other decreases.
• What does the correlation coefficient tell us?

  Strength and direction of a linear relationship.
• What is a correlation coefficient?

  A number between -1 and +1 and states how strong a correlation is between two variables and the direction of the correlation
• What is the correlation coefficient for a positive correlation?

  +1
• What is the correlation coefficient for a negative correlation?

  -1
• What is the correlation coefficient if the variables are unrelated?

  0
• What are the strengths of a correlation?

  • Can identify relationships without having to manipulate behaviour so it can be used in situations where experimentation would otherwise be unethical or impossible.
  • Quick and easy to interpret
  • Good starting point to suggest ideas for future experiments
• What are the weaknesses of correlations?

  • Cause and effect cannot be established
  • Other unknown variables may have caused the link between the variables being measured.