There are many advantages of non-parametric methods over parametric ones. The advantages can precisely be delineated as under:
Any inference based on the parametric analysis which does not uphold the underlying assumptions necessitated for it will be erroeneous.In such a situation non-parametric methods can safely be applied
If the measurement scale of data is nominal or ordinal, non-parametric methods can be used
In case the measurement are not so accurate as to apply parametric methods, non-parametric methods perform better
With so-called dirty data(contaminated observations,outliers,etc.,),many non-parametric methods are appropriate
There is no restriction for minimum size of sample for non-parametric methods for valid and reliable results
Non-parametric methods require minimum assumption like continuity of the sampled population
The analysis of data is simple and involves little computation work
Non-parametric test may be quite powerful even if the sample sizes are small
Non-parametric test are inherently robust against certain violation of assumptions
These are the reasons Non-parametric methods are widely used in research analysis than parametric methods.