I have a Healthcare dataset. I have been told to look at non-parametric approach to solve certain questions related to the dataset. I am little bit confused about non-parametric approach.

Do they mean density plot based approach (such as looking at the histogram)? I know this is a vague question to ask here. However, I don't have access to anybody else whom I can ask and hence I am asking for some input from others in this forum.

Any response/thought would be appreciated.

Thanks and regards.


1 Answer 1


They are not specifically referring to a plot based approach. They are referring to a class of methods that must be employed when the data is not normal enough or not well-powered enough to use regular statistics.

Parametric and nonparametric are two broad classifications of statistical procedures with loose definitions separating them:

  • Parametric tests usually assume that the data are approximately normally distributed.
  • Nonparametric tests do not rely on a normally distributed data assumption.
  • Using parametric statistics on non-normal data could lead to incorrect results.
  • If you are not sure that your data is normal enough or that your sample size is big enough (n < 30), use nonparametric procedures rather than parametric procedures.
  • Nonparametric procedures generally have less power for the same sample size than the corresponding parametric procedure if the data truly are normal.

Take a look at some examples of parametric and analogous nonparametric tests from Tanya Hoskin's Demystifying Summary:

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Here are some summary references:

  • 1
    $\begingroup$ Great answer @AN6U5. Appreciate your comments. Thanks... $\endgroup$
    – user62198
    Commented Jul 24, 2015 at 15:25

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