What is statistical significance?
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The effect found in a sample is statistically significant if the null hypothesis is rejected. If the null hypothesis is not rejected, then the effect is not significant.
Statistical significance (p-value) of a result indicates to which degree the result is “true” in terms of being representative of the population. In other words, it’s a probability that the observed relationship between variables (or a difference between means) in a sample occurred by pure chance.
A level of significance is selected prior to conducting statistical analysis. Traditionally, either the 0.05 level (sometimes called the 5% level) or the 0.01 level (1% level) is used. If the probability is less than or equal to the significance level, then the null hypothesis is rejected and the outcome is said to be statistically significant. The 0.01 level is more conservative than the 0.05 level.
The Greek letter alpha (α) is sometimes used to indicate the significance level.
Example / Application
Application: In the normal curve seen above, the shaded region represents the area in which the results are "significant".
Field, A. (2006). Discovering Statistics Using SPSS: Second Edition. London. Thousand Oaks. New Delhi. Sage Publication