Final answer:
When parametric assumptions are violated or the data are in the form of ranks, the method we use is Non-parametric tests.
Step-by-step explanation:
When parametric assumptions are violated or the data are in the form of ranks, the method we use is Non-parametric tests. Non-parametric tests do not assume a specific distribution of data and are suitable for situations where parametric assumptions are not met or when the data are in the form of ranks.