One Sample Wilcoxon Signed Rank Test

One Sample Wilcoxon Signed Rank Test

One Sample Wilcoxon Signed Rank Test is located under Model Studio () in Statistical Analysis below Hypothesis Test, under Non-Parametric Test in the left task pane. Use the drag-and-drop method or double-click to use the algorithm in the canvas. Click the algorithm to view and select different properties for analysis. You can access it using the search option.


Properties of One Sample Wilcoxon Signed Rank Test

The available properties of the One Sample Wilcoxon Signed Rank Test are shown below.


The table below describes the different properties of the One Sample Wilcoxon Signed Rank Test.

Field

Description

Remark

RunIt allows you to run the node.-
ExploreIt allows you to explore the successfully executed node.-
Vertical Ellipses

The available options are

  • Run till node
  • Run from node
  • Publish as a model
  • Publish code
-

Task Name


It is the name of the task selected on the workbook canvas.

  • You can click the text field to edit or modify the task's name.
  • Space between words is not allowed in the Task Name.

Features


It allows you to select the independent variable.

  • You need to select numeric data.
  • Only columns with numeric data will be shown.

Advanced

Hypothesized mean

It is the value that the test uses to determine if the group differs

The default value is 5. You can modify this value.


Zero Method

Zero difference is a way of telling whether you wish to discard the differences in your data or not.

  • For Zero difference, you can choose from 3 available methods.
  • Wilcox – It discards all zero differences.
  • Pratt – It includes the zero differences in the ranking process but drops the ranks of the zeros. For Pratt, the dataset must ideally have more than 20 data points.
  • Zsplit – It includes zero differences in the ranking process and splits the zero rank between positive and negative.
    The method selected by default is Wilcox.


Correction

  • If true, it means that we are applying the continuity correction.
  • We adjust the Wilcoxon rank statistic by 0.5 towards the mean value.
  • We do this while computing the z statistic.
  • The default value is False. You can modify this value.
  • If the correction is True, Continuity is applied and a normal approximation is used. This is done by adjusting the Wilcoxon rank statistic. This is done while computing the z-statistic in the case where a normal approximation is used.


Alpha

It allows you to set the level of significance.

  • The default value is 0.05. You can modify this value.
  • The value of alpha lies between 0 and 1. The value 0 interprets 100% confidence on the test. The value 1 interprets 0% confidence on the test. The system cannot guarantee both scenarios; hence the values cannot be 0 and 1.


Alternative

Defines the alternative hypothesis.

  • The default value is Two-sided. You can modify this value.
  • You can choose from –
  • Two-sided - the distributions are not equal
    • Larger- underlying x distribution is stochastically less than the underlying y distribution.
  • Smaller- underlying x distribution is stochastically greater than the underlying y distribution.

Node Configuration


It allows you to select the instance of the AWS server to provide control over the execution of a task in a workbook or workflow.

For more details, refer to Worker Node Configuration.

Example of One Wilcoxon Signed Rank Test

As a medical researcher, you would like to know if a given Drug 1 performs better than the determined level of 5. You use one sample Wilcoxon test to do so.

The data tab shows the selected input column and a new column called Difference which shows the values obtained after subtracting the hypothesized median, which is 5 in this case, from the input column.
Further, the Result page is as follows.

The result page consists of the following sections:

  1. Hypothesis:
    This section displays Null Hypothesis and Alternative Hypothesis defined by the system.
  2. One Sample Wilcoxon Signed Rank Test:
    This section displays the One-Sample Wilcoxon Signed Rank test result. It shows a value of the following parameters:
    • Population Median
    • Hypothesized Median
    • Test Statistic
    • p Value
    • Alpha (α)
  3. Interpretation:
    In this example, the p value (0.0001) is less than the alpha value (0.05); hence the null hypothesis is rejected. Thus, in this case, the level of effectiveness of drug 1 is more than 5.



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