Correlations

Question 1

Summarise correlations

Answer 1

Correlations measure the relationship between co-variables. Correlations can either be positive, negative or show no correlation

• Positive Correlation: the co-variables increase or decrease together.

• Negative Correlation: one variable increases; while the other decreases.

• Zero Correlation: there is no relationship between the two variables.
Look out for other patterns in the correlation: such as the relationship between the variables plateauing (levelling out).

Question 2

What are the strengths of correlation?

Answer 2

Correlations allow researchers to investigate situations that could not be done experimentally. They are used when it is practically or ethically impossible to manipulate the IV - in this case variables are simply measured

2. Preliminary research: Provide a means of conducting preliminary research as correlation studies can indicate trends which may lead to further research using experimental means to establish causal links. They are a useful and simple way of starting off a research project and can help to prevent time being wasted in carrying out unrealistic experiments.

Question 3

Limitations of correlations

Answer 3

1. Cannot establish cause and effect: correlations can only tell us how variables are related but not why. Correlations cannot demonstrate cause and effect between variables and therefore we do not know which co-variable is causing the other to change. Additionally, people often misinterpret correlations believing there to be a cause-and-effect relationship when one doesn’t exist.
2. Third variable problem There may be other unknown variables that can explain why the co-variables being studied are linked.

Question 4

What is a correlation coefficient?

Answer 4

A correlation coefficient is a number that tells us the strength and direction of the relationship between the two variables. This has to be calculated to determine the exact nature of the correlation. The coefficient is a number between +1 and -1 and is usually represented by the letter r or rs.

Question 5

What is the strength of a correlation given by?

Answer 5

The strength of correlation is given by how close the correlation coefficient is to +1 or -1. The sign indicates the type of correlation. If the correlation coefficient has a minus sign before it this means that it is a negative correlation, otherwise it is a positive correlation. Treat the
sign and the number separately. For example: r = +0.7 is the same strength as -0.7, with the
first being a positive correlation and the second being a negative.

Correlation coefficients between -0.1 and +0.1 are usually be judged to have zero/no correlation. Note that coefficients that appear to indicate a weak correlation can still be statistically significant: it depends on the size of the data set.