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Life in Freshwater


General advice for distressed non-statisticians


Plan your investigation in such a way as to make the results amenable to statistical analysis.

One of the peculiarities of examination boards (we are assuming that you are most probably doing A Level course work of some kind) is that they are very fond of hypothesis testing statistics. This means that if you want high marks, you have to include at least one statistical test on your data. As a result of this obsession, you need an adequately sized sample of either measurements of something or counts of something. If you are not sure how to justify your sample size see the section called "How big should a sample be?"

You can read all about hypothesis testing statistics in the section called "The structure of hypothesis testing statistics".

Don't worry if you end up accepting your null hypothesis. Just because you didn't find any difference or correlation doesn't mean it's all gone horribly wrong. In some ways it gives you more to write about in your discussion because you can say something along these lines: "Initial observations seemed to indicate that there would be a significant difference between penis/body length ratio in humans and barnacles because of....blah, blah, blah......The present investigation found this not to be the case. This may be because of.......blah, blah, blah..........."

You get to talk about what you initially thought and then discuss further why it didn't come out like that.

Remember that statistics of this kind tell you nothing about the biology/ecology of the situation. All they do is tell you something about numbers. It is up to you to interpret what it all means using your knowledge of biology and ecology. As a biologist/geographer/human being, this might be the bit that you find most stimulating.

It is important to remember that you MUST jump through the hoops specified by your examination boards specification. The specifications produced by exam boards tell you exactly what is required.

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