Correlations

• Correlations

  a correlation measures the relationship between two variables. This relationship can be positive or negative, strong or weak. Correlations have two variables of equal importance: these are called co-variables

  • a correlation is a statistical technique that can either be shown;

  -numerically as a correlation coefficient

  -pictorially as a scatter gram

  Correlations have no IV or DV (dont look for a cause and effect relationship, instead they look at patterns and trends). One variable doesnt necessarily directly cause a change in the other variable
• Positive and negative correlation

  positive correlation - as one variable increases, so does the other

  zero/no correlation - there is no correlation between the co-variables

  negative correlation - as one increases, the other decreases
• Correlation coefficients

  the correlation coefficient (r) is always between -1 and 1. The size of the coefficient represents the strength of the relationship between the two variables. The nearer to 1 or -1, the stronger the correlation

  • -1 = perfectly negative correlation
  • -0.8 = strong negative correlation
  • -0.3 = weak negative correlation
  • 0 = zero correlation
  • +0.3 = weak positive correlation
  • +0.8 = strong positive correlation
  • +1 = perfectly positive correlation

  the sign of the coefficient represents the direction of the relationship (whether it is positive or negative)
• Evaluation of Correlations

  Strength;

  • correlations are used when it is impractical to manipulate the independent variable
  • correlations are used when it is unethical to manipulate the independent variable

  Weakness;

  • correlations do not infer causation