The probability that the observed results occurred by chance. Generally, a p-value less than 0.05 suggests the result is "statistically significant." Choosing the Right Tool
The sheer volume of available tests exists because real-world data is messy. You might need a test for circular data (the ), a test for outliers (the Grubbs' test ), or a test for the equality of variances ( Levene's test ). Selecting the wrong test—such as using a parametric test on highly non-normal data—can lead to "Type I errors" (false positives) or "Type II errors" (false negatives). Conclusion 100 Statistical Tests
Regardless of which of the 100 tests is used, they almost all follow a unified logic: The assumption that there is no effect or difference. The Alternative Hypothesis ( H1cap H sub 1 ): The claim that there is a significant effect. The probability that the observed results occurred by chance