Correlations

Correlation

A technique that measures whether or not there is a relationship between two variables (co variables)

A correlation is shown

Graphically (scatter gram) or numerical representation (correlation coefficient)

Correlation coefficient

When correlation is represented mathematically by using a number between +1 and -1

Positive correlation

As one variable increase ses the value fo the other variable also increases. Directionally proportional

Weak positive correlation

When the r is +0.2

Strong positive correlation

When r is +0.9

Negative correlation

As one variable increases the other variables decreases. Inversely proportional

Weak negative correlation

When r is -0.2

Strong negative correlation

When r is -0.9

Zero/no correlation

When the two variables aren’t related at all. Shows no relationship between the two variables. Anything close to zero

Zero correlation on correlation coefficients

When r is -0.02 and when r is +0.05 there is no correlation

Significance of correlation

Significant correlations indicate that there is a relationship not why or how. Correlation doesn’t show cause and effect

The 3 possible explanations for the significance of correlation

Casualty - one variable caused the other to change, chance - variables just happened to be related, third factor involved - intervening variable

Intervening variable

Another variable is causing the relationship

First strength of correlation

P - Allow you measure things that can’t be manipulated experimentally (unethical). E - Can make use of existing data. L - Beneficial, psychologists can carry out research without any ethical issues

Second strength of correlation

P - Can suggest trends that can lead to experiments. E - Require little effort, less time consuming than experiments. L - Beneficial, saves time and money

First weakness of correlation

P - Don’t allow you to establish cause and effect. E - Correlation = association between 2 variables could be a 3rd. L - Could lead to serious misunderstandings

Second weakness of correlation

P - Limited by the method used to collect data. E - Ex using questionnaires can lack internal validity from social desirability bias. L - An issue, the correlation could lack validity