# Difference Between Parametric And Nonparametric Statistical Tests Pdf

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To make the generalisation about the population from the sample, statistical tests are used.

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Topics: Hypothesis Testing , Statistics. That sounds like a nice and straightforward way to choose, but there are additional considerations. Nonparametric tests are like a parallel universe to parametric tests. The table shows related pairs of hypothesis tests that Minitab Statistical Software offers. Reason 1: Parametric tests can perform well with skewed and nonnormal distributions. This may be a surprise but parametric tests can perform well with continuous data that are nonnormal if you satisfy the sample size guidelines in the table below.

These guidelines are based on simulation studies conducted by statisticians here at Minitab. To learn more about these studies, read our Technical Papers. Reason 2: Parametric tests can perform well when the spread of each group is different. For nonparametric tests that compare groups, a common assumption is that the data for all groups must have the same spread dispersion.

If your groups have a different spread, the nonparametric tests might not provide valid results. Parametric tests usually have more statistical power than nonparametric tests.

Thus, you are more likely to detect a significant effect when one truly exists. For these two distributions, a random sample of from each distribution produces means that are significantly different, but medians that are not significantly different. When you have a really small sample, you might not even be able to ascertain the distribution of your data because the distribution tests will lack sufficient power to provide meaningful results.

Typical parametric tests can only assess continuous data and the results can be significantly affected by outliers. Conversely, some nonparametric tests can handle ordinal data, ranked data, and not be seriously affected by outliers. Be sure to check the assumptions for the nonparametric test because each one has its own data requirements. This can be the case when you have both a small sample size and nonnormal data.

However, other considerations often play a role because parametric tests can often handle nonnormal data. Finally, if you have a very small sample size, you might be stuck using a nonparametric test. Please, collect more data next time if it is at all possible! Your chance of detecting a significant effect when one exists can be very small when you have both a small sample size and you need to use a less efficient nonparametric test!

Minitab Blog. Nonparametric analysis to test group medians. Hypothesis Tests of the Mean and Median Nonparametric tests are like a parallel universe to parametric tests. Parametric analyses Sample size guidelines for nonnormal data 1-sample t test Greater than 20 2-sample t test Each group should be greater than 15 One-Way ANOVA If you have groups, each group should be greater than If you have groups, each group should be greater than Reason 3: Statistical power Parametric tests usually have more statistical power than nonparametric tests.

If the mean accurately represents the center of your distribution and your sample size is large enough, consider a parametric test because they are more powerful. If the median better represents the center of your distribution, consider the nonparametric test even when you have a large sample. You Might Also Like. Statistics 5 Minute Read. Statistics 4 Minute Read.

All rights reserved. By using this site you agree to the use of cookies for analytics and personalized content in accordance with our Policy. Parametric tests means. Nonparametric tests medians. Factorial DOE with one factor and one blocking variable.

Sample size guidelines for nonnormal data.

## Difference Between Parametric and Nonparametric Test

Mesquita, Sulin Tao, Triphonia J. Box , Kampala, Uganda. Box , Dar-es-Salaam, Tanzania. Numerical models are presently applied in many fields for simulation and prediction, operation, or research. The output from these models normally has both systematic and random errors. The study compared January temperature data for Uganda as simulated using the Weather Research and Forecast model with actual observed station temperature data to analyze the bias using parametric the root mean square error RMSE , the mean absolute error MAE , mean error ME , skewness, and the bias easy estimate BES and nonparametric the sign test, STM methods.

ANOVA vs. a non-parametric test. Some of the most common statistical tests and their non-parametric analogs: For nonparametric tests that compare.

## Comparison of Parametric and Nonparametric Methods for Analyzing the Bias of a Numerical Model

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First of all, it is better to know each of them, then I want to elaborate to find the majors differences between both of them, in details. Indeed, inferential statistical procedures generally fall into two possible categorizations: parametric and non-parametric. In the literal meaning of the terms, a parametric statistical test is one that makes assumptions about the parameters defining properties of the population distribution s from which one's data are drawn, while a non-parametric test is one that makes no such assumptions. In this strict sense, "non-parametric" is essentially a null category, since virtually all statistical tests assume one thing or another about the properties of the source population s.

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The three modules on hypothesis testing presented a number of tests of hypothesis for continuous, dichotomous and discrete outcomes. Tests for continuous outcomes focused on comparing means, while tests for dichotomous and discrete outcomes focused on comparing proportions. All of the tests presented in the modules on hypothesis testing are called parametric tests and are based on certain assumptions.

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Quantitative Methods 2 Reading Hypothesis Testing Subject Parametric and Non-Parametric Tests.

Need a hand? All the help you want just a few clicks away. Therefore, several conditions of validity must be met so that the result of a parametric test is reliable. They can thus be applied even if parametric conditions of validity are not met. Parametric tests often have nonparametric equivalents.

#### Key Differences Between Parametric and Nonparametric Tests

Topics: Hypothesis Testing , Statistics. That sounds like a nice and straightforward way to choose, but there are additional considerations. Nonparametric tests are like a parallel universe to parametric tests. The table shows related pairs of hypothesis tests that Minitab Statistical Software offers. Reason 1: Parametric tests can perform well with skewed and nonnormal distributions. This may be a surprise but parametric tests can perform well with continuous data that are nonnormal if you satisfy the sample size guidelines in the table below. These guidelines are based on simulation studies conducted by statisticians here at Minitab.

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## Mindy R.

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