We talked about hypotheses in the previous blog. Let’s just summarise:
The aim is the purpose of the study, but isn’t usually in precise enough terms to test. So we need a hypothesis. A hypothesis is a testable statement. A research hypothesis is generated by a theory. It is developed to test a theory.
A null hypothesis is what we assume to be true when carrying out psychological research. It doesn’t mean that this is what a psychologist believes to be true though. It can simply be used as a hypothesis for the purpose of the research. For example, I may believe that women are better drivers than men. A null hypothesis to test this belief would state “There is no difference between male and female driving ability.”
I would then carry out research to test that null hypothesis. At the end of the research, if I found that women were better drivers, this would show that the null hypothesis was wrong, so we would reject the null hypothesis. We have proved it is wrong.
If I found that the null hypothesis was right – that there was no difference between male and female drivers – then the null hypothesis would be found to be true.
A null hypothesis often predicts that there is no relationship between the variables in the research and that any result is due to chance. The hypothesis that “There is no difference between male and female driving ability” is an example of a null hypothesis that suggests no difference.
A directional hypothesis suggests that two variables are linked. The hypothesis that “Women will perform better in a driving test than men” is an example of a directional hypothesis. The hypothesis suggests what is going to happen and the direction in which it will happen, i.e. that women will be better drivers and the direction of the results will show this. So if I found that women were better drivers, it would prove my hypothesis. If I found men were better drivers, it would disprove my hypothesis.
Directional hypotheses often use previous research to suggest the way that the results will go.
A non-directional hypothesis will predict that there will be a difference between two groups, but won’t predict in which direction. For example, “There will be a difference in male and female performance in a driving test”: this hypothesis does not say whether men will perform better or women will perform better.
Often non-directional hypotheses are used when there is little previous research on a particular topic or the previous search did not come to any particular conclusion.