Definition: n = number in a trial or sample. SAMPLE SIZE Why is sample size important? The aim of statistical testing is to uncover a significant difference when it actually exists. In its simplest form this involves comparing samples between one regime and another (which may be a control). Sample size is important because Larger samples increase the chance of finding a significant difference, but Larger samples cost more money. Why does a larger sample size help? The sample size is chosen to maximise the chance of uncovering a specific mean difference, which is also statistically significant. Please note that specific difference and statistically significant are two quite different ideas. The specific difference is chosen by the researcher in terms of the outcome measure of the experiment. For instance, 3kg mean weight change in a diet experiment, 10% mean improvement in a teaching method experiment. Statistical significance is a probability statement telling us how likely it is that the observed difference was due to chance only.
Posted on: Tue, 18 Jun 2013 06:26:35 +0000
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