The importance of the null hypothesis.

with 5 comments

When researchers carry out studies it is the null hypothesis they are testing, not the research hypothesis. The null hypothesis states that there will be no difference between the groups being tested so the means of the groups will be exactly the same. In comparison the research hypothesis states that there is a difference between the groups. With the null hypothesis declaring that there is no difference between samples then there are two possible outcomes, there is or is not a difference. However if you were to test the research hypothesis there would be so many possible outcomes it would be near impossible to test.

In order to see if there actually is a difference we need to examine how different the two groups actually are. We do this by looking at the variability within groups and between groups. The more different the individuals are in a group the more difference there needs to be between groups in order for there to be a difference overall. To work out the difference between groups you have to divide between group variance by within group variance. Ideally you want large between group variance and small within group variance, so the standard deviation is clustered tightly around the mean. Most commonly researchers find that they have small between group variance and small within group variance, meaning a smaller effect size. The less overlap there is between the distributions the more likely you are to find a significant difference.

In conclusion we need the null hypothesis to determine if there is a difference between groups being tested or not. Without it we would be swamped with possibilities making it almost impossible to test.


Written by amw1992

October 28, 2011 at 2:36 pm

Posted in Uncategorized

5 Responses

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  1. I agree that the null hypothesis is needed and important when conducting research. Without using the null hypothesis in research, you could not do the statistical hypothesis test. When you do he statistical hypothesis test you reject or fail to reject the hypothesis, (Howitt & Cramer, 2011). Despite there being a lot of evidence for a theory (such as the theory of gravity) there is no proof that more evidence may come along in the future and it can not be generated to the population therefore, we aim to reject the hypothesis an not prove the hypothesis. Therefore the null hypothesis is important.

    Howitt, D. & Cramer, D. (2011). Introduction to Research Methods in Psychology, third edition. Pearsons Education.


    October 28, 2011 at 5:07 pm

  2. There is also one more importance of the null hypothesis and that is its falsifiability. The example that everyone uses is that you only need to find one black swan to disprove the theory that all swans are white. much easier than going around and staring at every single swan around. That’s the main use of the null as part of the scientific method without the null it would be virtually impossible to progress in science!,


    November 21, 2011 at 5:59 pm

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