Data considerations for 1-Sample Wilcoxon

To ensure that your results are valid, consider the following guidelines when you collect data, perform the analysis, and interpret your results.

The data should come from a symmetric distribution, such as the uniform or Cauchy distributions

If your data do not come from a symmetric distribution, use 1-Sample Sign.

The data do not need to be normally distributed

However, if you have more than 20 observations or your data aren't severely skewed, use 1-Sample t because the test has more power.

The sample data should be selected randomly

In statistics, random samples are used to make generalizations, or inferences, about a population. If your data are not collected randomly, your results may not represent the population. For more information, go to Randomness in samples of data.

Each observation should be independent from all other observations

The independence of observations is determined by whether one observation provides information about another observation, as follows:

If an observation provides no information about the value of another observation, the observations are independent.
If an observation provides information about another observation, the observations are dependent. If your observations are dependent, your results may not be valid.