Difference Between Parametric and Non-Parametric Test

Parametric vs Nonparametric Tests

Parametric is a test in which parameters are assumed and the population distribution is always known. To calculate the central tendency, a mean value is used. These tests are common, and this makes performing research pretty straightforward without consuming much time. No assumptions are made in the Non-parametric test and it measures with the help of the median value. A few instances of Non-parametric tests are Kruskal-Wallis, Mann-Whitney, and so forth. In this article, you will be learning what is parametric and non-parametric tests, the advantages and disadvantages of parametric and nan-parametric tests, parametric and non-parametric statistics and the difference between parametric and non-parametric tests.

What is a Parametric Test?

In Statistics, the generalizations for creating records about the mean of the original population is given by the parametric test. This test is also a kind of hypothesis test. A t-test is performed and this depends on the t-test of students, which is regularly used in this value. This is known as a parametric test.

The t-measurement test hangs on the underlying statement that there is the ordinary distribution of a variable. Here, the value of mean is known, or it is assumed or taken to be known. The population variance is determined in order to find the sample from the population. The population is estimated with the help of an interval scale and the variables of concern are hypothesized. 

What is a Non-Parametric Test?

There is no requirement for any distribution of the population in the non-parametric test. Also, the non-parametric test is a type hypothesis test that is not dependent on any underlying hypothesis. In the non-parametric test, the test depends on the value of the median. This method of testing is also known as distribution-free testing. Test values are found based on the ordinal or the nominal level. The parametric test is usually performed when the independent variables are non-metric. This is known as a non-parametric test.

Differences Between The Parametric Test and The Non-Parametric Test

Properties

Parametric Test

Non-Parametric Test

Assumptions

Yes, assumptions are made

No, assumptions are not made

Value for central tendency

The mean value is the  central tendency

The median value is the  central tendency

Correlation

Pearson Correlation

Spearman Correlation

Probabilistic Distribution

Normal probabilistic distribution

Arbitrary probabilistic distribution

Population Knowledge

Population knowledge is required

Population knowledge is not required

Used for

Used for finding interval data

Used for finding nominal data

Application

Applicable to variables

Applicable to variables and attributes

Examples

T-test, z-test

Mann-Whitney, Kruskal-Wallis


Advantages and Disadvantages of Parametric and Nonparametric Tests 

A lot of individuals accept that the choice between using parametric or nonparametric tests relies upon whether your information is normally distributed. The distribution can act as a deciding factor in case the data set is relatively small. Although, in a lot of cases, this issue isn't a critical issue because of the following reasons:: 

  • Parametric tests help in analyzing nonnormal appropriations for a lot of datasets. 

  • Nonparametric tests when analyzed have other firm conclusions that are harder to achieve.

The appropriate response is usually dependent upon whether the mean or median is chosen to be a better measure of central tendency for the distribution of the data. 

  • A parametric test is considered when you have the mean value as your central value and the size of your data set is comparatively large. This test helps in making powerful and effective decisions.

  • A non-parametric test is considered regardless of the size of the data set if the median value is better when compared to the mean value. 

Ultimately, if your sample size is small, you may be compelled to use a nonparametric test. As the table shows, the example size prerequisites aren't excessively huge. On the off chance that you have a little example and need to utilize a less powerful nonparametric analysis, it doubly brings down the chances of recognizing an impact.

The non-parametric test acts as the shadow world of the parametric test. In the table that is given below, you will understand the linked pairs involved in the statistical hypothesis tests. 

Related Pairs of Parametric Test and Non-Parametric Tests

Parametric Tests for Means

Non-Parametric Test for Medians

1 - sample t - test

1 - sample Wilcoxon, 1 - sample sign

2 - sample t - test

Mann - Whitney Test

One - way ANOVA

Kruskal- Wallis, Mood’s median test

With a factor and a blocking variable - Factorial DOE

Friedman Test

FAQ (Frequently Asked Questions)

1. What is a Parametric Test?

In Statistics, the generalizations for creating records about the mean of the original population is given by the parametric test. This test is also a kind of hypothesis test. A t-test is performed and this depends on the t-test of students, which is regularly used in this value. This is known as a parametric test. The t-measurement test hangs on the underlying statement that there is the ordinary distribution of a variable. Here, the value of mean is known, or it is assumed or taken to be known. The population variance is determined in order to find the sample from the population. The population is estimated with the help of an interval scale and the variables of concern are hypothesized.

2. What is a Non-parametric Test?

There is no requirement for any distribution of the population in the non-parametric test. Also, the non-parametric test is a type hypothesis test that is not dependent on any underlying hypothesis. In the non-parametric test, the test depends on the value of the median. This method of testing is also known as distribution-free testing. Test values are found based on the ordinal or the nominal level. The parametric test is usually performed when the independent variables are non-metric. This is known as a non-parametric test.