Correlation

    Cards (7)

    • Correlations are used to test a relationship between 2 variables & experiments are a test of difference.
    • Correlational analysis- used to investigate the relationship between 2 variables, eg obesity & heart attacks.
    • Carrying out correlational analyses:
      1. Decide which variables you want to study, eg height & shoe size.
      2. Set a hypothesis- directional or non-directional hypothesis, if it's directional you are predicting the direction of the relationship.
      • Positive correlation= as one increases, so does the other
      • Negative correlation= as one increases, the other decreases
      • No correlation= no relationship/ association shown
    • Calculating the correlation co-efficient:
      • This is a statistical technique which allows you to see if your relationship is strong enough to be significant, ie worth basing a conclusion on.
      • It gives the correlation a value from +1 to -1.
      • The closer the value is to +1 or -1, the stronger the relationship.
      • Zero indicates no relationship (& a positive isn't better than a negative, they just show different relationships).
    • Correlational analysis Strengths:
      • Easy, quick, economical method, just need two sets of data (often collected by someone else like the government), no manipulation of variables, no need for controlled environment.
      • May form the basis for further research.
      • Can study relationships that it would be unethical to purposely manipulate (eg links between stress & illness).
    • Correlational analysis Weaknesses:
      • Impossible to infer cause & effect, as IV is not manipulated.
      • Other variables could cause the relationship measured.
      • Only measures linear relationships- such a relationship would have a low correlation co-efficient but it is actually very strong.