Psychology AS OCR (investigations) - Correlations

There are three types of correlations :

Postive Correlation- As one variable increases, so does the other. (the closer to +1, the stronger the positive correlation)

Eg. The bigger the height of a person, the larger their shoe size.

Negative Correlation - As one variables increases, the other decreases. (the closer to -1, the stronger the negative correlation)

Eg. The more alcohol consumed, the worse the driving performance.

No(zero) Correlation - No relationship between the two variables.

+ Can be used where experimental manipulation would be unethical or impossible.

+ Can suggest further avenues of research.

+ When only one variable is known, the other can be predicted.

- It only examines the strength of the relationship between the two variables not a cause and effect between variables.

- The relationship may be effected by extraneous variables.

- Correlation coefficients overlook relationships that are not linear.

The closer a correlation coefficient is to 1,the stronger the correlation is. The sign doesnt matter, +1 is as strong as -1.

Correlation Coefficient Value                          Strength of the Relationship

1.0                                                                      Perfect positive

0.8                                                                      Strong positive

0.5                                                                       Moderate positive

0.3                                                                       Weak positive

0.1                                                                       Very weak positive

0                                                                          No relationship

-0.1                                                                      Very weak negative

-0.3 etc                                                                 Weak negative