What is paramtric and non-paramtreic?

Answer 1

In statistics, an underlying assumption of parametric tests or analyses is that the dataset on which you want to use the test has been demonstrated to have a normal distribution. That is, estimation of the "parameters", such as mean and standard deviation, is meaningful. For instance you can calculate the standard deviation of any dataset, but it only accurately describes the distribution of values around the mean if you have a normal distribution.

If you can't demonstrate that your sample is normally distributed, you have to use non-parametric tests on your dataset.