 Statistics is a crucial tool for making sense of data and drawing conclusions about populations. Non-parametric statistical tests are particularly useful when the assumptions of parametric tests are not met or when data is non-normal. However, non-parametric tests can be challenging to interpret and perform, and many researchers may need help to use them effectively. There are many reasons why one may need help with non-parametric statistical tests. For example, understanding the underlying theory can be challenging for those without a background in statistics. Non-parametric tests in data analysis are based on different principles than parametric tests and rely on ranks, medians, and other non-parametric measures. Choosing the appropriate test can also be challenging, as there are many types of non-parametric tests, each used for a different purpose. Interpreting the results of non-parametric tests can be particularly difficult, as they do not provide p-values that can be directly compared to a significance level. Instead, non-parametric tests provide test statistics that need to be interpreted in the context of the research question and data set. Additionally, non-parametric tests require complete data sets, and missing data can be challenging to deal with. Calculating effect sizes for non-parametric tests can also be challenging, as they do not provide effect sizes in the same way that parametric tests do. Instead, effect sizes need to be calculated using non-parametric measures, such as Cohen's d or the odds ratio. Choosing the appropriate software to perform non-parametric tests can also be challenging, especially for those without a background in statistics. Look at these and other reasons why one may need help with non-parametric statistical tests. We will also discuss the benefits of seeking help from a statistician or statistical software and provide tips for using non-parametric tests effectively.

### Reasons for Seeking Help with Non-Parametric Statistical Tests

1. Understanding the underlying theory: Non-parametric tests are based on different principles than parametric tests since they rely on ranks, medians, and other non-parametric measures, rather than assuming a normal distribution. Understanding the fundamental theory of these tests can be challenging for those without a background in statistics and thus need a statistician or a statistical software program.
2. Choosing the appropriate statistical test: There are many types of non-parametric tests, including the Wilcoxon signed-rank test, the Mann-Whitney U test, and the Kruskal-Wallis test, among others, and each test is used for a different purpose, and choosing the appropriate test can be challenging but not for experts with skills in choosing the appropriate test for the research question and data set.
3. Interpreting the results: Unlike parametric tests, non-parametric tests do not provide p-values that can be directly compared to a significance level. Instead, non-parametric tests provide test statistics that need to be interpreted in the context of the research question and data set which statisticians can be useful.
4. Dealing with missing data: Non-parametric tests require complete data sets, and missing data can be challenging to deal with. Some non-parametric tests, such as the Wilcoxon signed-rank test, can handle missing data, but others cannot and that is where a statistician come in to help deal with missing data in a way that is appropriate for the chosen non-parametric test.
5. Calculating effect sizes: The effect sizes need to be calculated using non-parametric measures, such as Cohen's d or the odds ratio which can be challenging for those without skills in statistics hence needing skilled statistician help with these calculations.
6. Choosing the appropriate software: There are many statistical software programs available, such as R, SPSS, and SAS, that can perform non-parametric tests but choosing the appropriate software can be challenging in which a statistician can help choose the appropriate software for the research question and data set.
7. Dealing with large data sets: Some non-parametric tests, such as the bootstrap method, can handle large data sets, but others cannot unlike statisticians who can help deal with large data sets in a way that is appropriate for the chosen non-parametric test.
8. Dealing with multiple comparisons: They can lead to an increased risk of false positives, and adjustments need to be made to account for this getting experts help can be appropriate for the preferred test.

Non-parametric statistical tests are essential tools for analyzing data that do not meet the assumptions of parametric tests. However, performing and interpreting these tests can be challenging, especially for those without a background in statistics. Choosing the appropriate test, interpreting the results, dealing with missing data, calculating effect sizes, choosing the appropriate software, dealing with large data sets, and handling multiple comparisons are all reasons why help may be needed with non-parametric statistical tests. Seeking help from a statistician or statistical software can ensure that these tests are performed and interpreted correctly and can lead to more accurate and reliable results. Understanding the reasons for seeking help with non-parametric tests can help researchers make more informed decisions and ensure that their research is conducted effectively.

## Application of Non-Parametric Test – Expert Guidance When Analyzing data, you can use non-parametric tests (statistical techniques) which are widely used in various fields such as medicine, social sciences, engineering, and more. These tests are essential when the data does not meet the assumptions of normality or equal variances required by parametric tests. Non-parametric tests are distribution-free tests and do not require the data to be normally distributed, making them more versatile and applicable to different types of data. Non-parametric tests are used to test for differences between independent and dependent samples, an association between two variables, goodness of fit, independence between categorical variables, homogeneity of variance, and trend. These tests are especially useful when the data is ordinal, non-linear, or not normally distributed. The Mann-Whitney U test, Wilcoxon signed-rank test, and Kruskal-Wallis test are some of the most common non-parametric tests used to test for differences in independent and dependent samples. The Spearman rank correlation coefficient is used to measure the strength and direction of the relationship between two variables. The chi-squared test and Fisher's exact test are used to test for goodness of fit and independence between categorical variables, respectively. Levene's test is used to test for homogeneity of variance, and the Jonckheere-Terpstra test is used to test for trend. Non-parametric tests are a valuable tool for analyzing data when the assumptions of parametric tests are not met. These tests are widely applicable in various fields and provide valuable insights into the relationships between variables. Understanding the application of non-parametric tests is essential for researchers and analysts who deal with non-normally distributed data.

### How to Use Non-Parametric Tests to Analyze Research Data

• Testing for Differences in Independent Samples: Non-parametric tests can be used to test for differences between two or more independent samples. The Mann-Whitney U test is one such non-parametric test that can be used to determine whether two independent groups have different median values which is useful when data does not meet the assumptions of normality or equal variances required by parametric tests.
• Checking for Differences in Dependent Samples: The Wilcoxon signed-rank test is used to determine whether two dependent groups have different median values. This test is commonly used in clinical trials to compare the effectiveness of different treatments.
• Testing for Variables Association: A Spearman rank correlation coefficient is a non-parametric test that can be used to measure the strength and direction of the relationship between two variables which is useful when data is ordinal or when the relationship between variables is non-linear.
• Measuring the Goodness of Fit: The chi-squared test is a non-parametric test that can be used to determine whether the observed frequency distribution of a categorical variable is significantly different from the expected frequency distribution which mostly applies to quality control ensuring that a product or process meets the desired specifications.
• Reviewing for Independence: The Fisher's exact test is a test that can be used to determine whether there is a significant association between two categorical variables mostly used in medical research to determine whether a particular treatment is associated with a certain outcome.
• Looking for Homogeneity of Variance: Levene's test helps to determine whether the variances of two or more groups are equal which is commonly used in analysis of variance (ANOVA) to determine whether there are significant differences between groups.
• Analyzing the Trend: The Jonckheere-Terpstra test is key to determining whether there is a trend in the response variable across ordered groups in social sciences to determine whether there is a trend in public opinion on a particular issue.

These tests are a valuable tool for analyzing data in various fields where data does not meet the assumptions of normality or equal variances required by parametric tests. These tests provide an alternative way of analyzing data, making them useful in situations where data is not normally distributed. The application of non-parametric tests includes testing for differences in independent and dependent samples, testing for association, testing for goodness of fit, testing for independence, testing for homogeneity of variance, and testing for trend. These tests can provide valuable insights into the relationships between variables and help researchers make informed decisions. Non-parametric tests have become increasingly popular in recent years, and their application is expected to continue to grow in the future.

## Assumptions of Parametric and Non-parametric Tests – Best Help Statistical tests are an essential part of data analysis in various fields, including business, psychology, and social sciences. Parametric and nonparametric tests are two commonly used types of statistical tests that differ in their assumptions and procedures. Understanding the assumptions of these tests is crucial to ensure the validity and accuracy of the results obtained from them. Parametric tests assume that the data being analyzed follows a normal distribution. These tests are based on the assumption that the population from which the sample is taken is normally distributed. Some examples of parametric tests include t-tests, ANOVA, and regression analysis. Nonparametric tests, on the other hand, do not assume a specific distribution of the data. These tests are based on the ranking of data, rather than on the numerical values of the data. Some examples of nonparametric tests include the Wilcoxon rank-sum test, the Mann-Whitney U test, and the Kruskal-Wallis test. The assumptions of parametric and nonparametric tests include normality, homogeneity of variance, independence, and linearity for parametric tests, and random sampling, independence, and ordinal data for nonparametric tests. Violation of these assumptions can lead to incorrect conclusions and invalid results. Study in detail the assumptions of parametric and nonparametric tests and the differences between them. We will also explore how violating these assumptions can impact the results of statistical tests. Understanding the assumptions of these tests is essential to ensure the appropriate selection of statistical tests and to avoid errors in data analysis.

### What are the Assumptions of parametric and nonparametric tests?

Assumptions of Parametric Tests
Parametric tests are statistical tests that assume that the data being analyzed follows a normal distribution. These tests are also known as distribution-based tests. Some of the assumptions of parametric tests include:
1. Normality: The data should follow a normal distribution, which means that the mean, median, and mode are equal.
2. Homogeneity of variance: The variance of the data should be equal across different groups or conditions being compared.
3. Independence: The observations in the sample should be independent of each other.
4. Linearity: There should be a linear relationship between the independent and dependent variables.

Some common parametric tests include t-tests, ANOVA, and regression analysis.

Assumptions of Nonparametric Tests
Nonparametric tests, on the other hand, do not assume a specific distribution of the data. These tests are also known as distribution-free tests. Some of the assumptions of nonparametric tests include:
1. Random sampling: The data should be obtained through random sampling.
2. Independence: Observations in the sample should be independent of each other.
3. Ordinal data: The data should be measured on an ordinal scale or higher.

Some common nonparametric tests include the Wilcoxon rank-sum test, the Mann-Whitney U test, and the Kruskal-Wallis test.

### What is the difference between parametric & nonparametric tests?

The main difference between parametric and nonparametric tests is in the assumptions they make about the data. Parametric tests for research data assume that the data follows a normal distribution, while nonparametric tests do not assume a specific distribution. Other differences between these two types of tests include:
1. Statistical power: Parametric tests have greater statistical power than nonparametric tests when the data meet the assumptions meaning that parametric tests can detect smaller differences between groups or conditions than nonparametric tests.
2. Sample size: In most cases. parametric tests are more reliable when the sample size is large as nonparametric tests are generally used when the sample size is small.
3. Type of data: Parametric tests are used for interval or ratio data, while nonparametric tests are used for ordinal or nominal data.
4. Assumptions: Parametric tests have more assumptions than nonparametric tests, which means that they are more sensitive to violations of these assumptions. Nonparametric tests are more robust to violations of assumptions.

The assumptions of parametric and nonparametric tests are crucial in determining which statistical test to use for a given dataset. Parametric tests assume that the data is normally distributed, while nonparametric tests do not make such assumptions. The assumptions of normality, homogeneity of variance, independence, and linearity are critical for parametric tests, while random sampling, independence, and ordinal data are necessary for nonparametric tests. Understanding these assumptions is essential to ensure that the chosen test is appropriate for the data and to obtain accurate and reliable analysis results. Violations of these assumptions can lead to incorrect conclusions and misleading results. Therefore, it is important to carefully consider the assumptions of each test before selecting the appropriate statistical test for the data being analyzed.