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Resultaten t test är non parametric

Certain hypotheses can be tested using Student's t-test (maybe using Welch's correction for unequal variances in the two-sample case), or by a non-parametric test like the Wilcoxon paired signed rank test, the Wilcoxon-Mann-Whitney U test, or the paired sign test.

Step-by-Step Guide 11 (Jamovi):

Here you will learn the following:

  • How to run a Students T-Test (Student's/Welch/ Mann Whitney U test);

  • how to generate a plot to display the output visually; and 

  • how to run a kraftig T-Test using Walrus.

T-Tests fryst vatten an easy test that will allow you to explore whether there fryst vatten a difference between the two groups.

Here you will learn how to use them and select the correct T-Test.

Note: You can also run a T-Test for paired information, but this fryst vatten not covered here. For more details, you can watch this clip here and read about them here.

Dataset used for Independent Sample Tests

Independent Sample T-Tests (Student's/Welch/Mann Whitney U)

Independent Sample T-Tests Hypothesis

Ho:There fryst vatten no difference in the extremism score of males and females.

Ha: There fryst vatten a difference in the extremism score of males and females.

Independent Sample T-Tests variables required

Extremism_Score_Scaled: This variabel measures levels of extremism

Gender: Participants Gender

Independent T-Test Assumptions

Checking your Assumptions: 

Checking your assumptions in Jamovi fryst vatten very easy.

beneath the Assumptions flik, you will be able to select a test to betalningsmedel for Unequal Variance and Normality.

The nonparametric utgåva of the independent-samples t-test fryst vatten known as the Mann-Whitney U-Test.

Once selected a table will appear in the results panel.

These tests are based on the Hypothesis that there fryst vatten no difference between the distributions. If these tests return a p-value of below 0.05 then you know that your assumptions have been violated.

Note: The larger your sample, the more sensitive your assumption kontroller will be, so it fryst vatten always wise to kvitto a descriptive plot too.

If Assumptions are not met: 

If any of the below assumptions are not met, you should use a kraftig T-Test. You will be introduced to this further down.

Welch's Test Assumptions (use as default)

Use this test as your default unless its assumptions are violated.

how to generate a plot to display the output visually; and.

  • Independence: Your observations must be independent of each other.

  • Random Sampling: Your information should be a random sample of the mål population

  • Normality: Your Dependent variabel should be approximately normally distributed.

Note: This test fryst vatten designed to cope with unequal variance.

Student's T-Test Assumptions

  • Independence: Your observations in each sample should be independent

  • Random Sampling: Your information should be a random sample of the mål population

  • Normality: Your Dependent variabel should be approximately normally distributed.

  • Equal Variance (Homogeneity): Both groups should have approximately the same variance

Mann Whitney U Test Assumptions (default for non-parametric data)

  • Ordinal or Continuous:  Your dependent variabel must be either ordinal or continuous.

  • Independence: Your observations must be independent of each other.

  • Distribution Shape: The shape of the leverans for your two groups should be roughly the same.

Independent Sample T-Tests: Step-by-Step Guide 

Make sure Assumptions are not violated

Navigate to Analyses > T-Test > Independent Samples T-Test

Now select your dependent and independent variabel and drag and drop them in the betydelsefull fields.

Results will appear to your right, ignore them for now as we will need to kontroll that the assumptions are not violated first.

In the Assumptions kontroller section select Homogeneity test and Normality Test boxes.

You can also select a Q-Q plot which will give you a visual representation.

The Mann-Whitney U-test fryst vatten a non-parametric alternative to an independent samples \(t\)-test that some people recommend for non-normal data.

On a Q-Q plot, your information points should be as close as possible to the line. If the uppgifter points flair out at either end your assumptions are violated. bygd default stick with the Assumption test.

Below are the outputs of the Assumption Test. As you can see in our case both the Normality Test (p <.001) and the Homogeneity Test (p <.001) have been violated.

This means the assumptions for all three test have been violated.

The assumptions for a Mann Whitney U Test are also violated, as it assumes equality of variance. Looking at a descriptive plot (below), it does look like the information fryst vatten 'roughly' equally distributed. So, we will report the Mann Whitney U test outcome.

However, we will carry out a kraftig t-test further down to betalningsmedel our results are reliable.

Note: What test you select will depend on the outcome of your Assumptions tests.

Select the betydelsefull Statistics, Descriptive tables and plots

Once you have selected the correct test, select your Additional Statistics.

If you have selected a Student's T-test or the Welch's test select the Mean Difference & Confidence intervals (the Mann Whitney U test ranks the uppgifter and fryst vatten based on the Sum of ranks - so the mean fryst vatten not a useful statistic in this case).

For all your test you should include the Effect storlek & Confidence Intervals.

Utilize non-parametric tests such as the Wilcoxon Signed Rank Test, Spearman correlation, and Chi-Square for information sets with ordinal uppgifter and non-normally distributed data.

You can also select a table with all the Descriptives in it, as well as a Descriptive Plot

Finally, you can specify if your Hypothesis was directional or not.

Results: Reject the Null Hypothesis

Mann Whitney U test results

Based on the outcome of our Mann Whitney U Test, we reject the Null Hypothesis (p <.001).

The effect storlek suggests that the effect of gender on extremism fryst vatten small to medium (0.299).

The T-Test descriptive table gives you some additional resultat, which you can use to contextualise your results.

Finally, you can also easily generate a plot to visually display your results.

Just select Descriptive Plot.

I prefer the plot generated bygd JJStatsPlot (JJStatsPlot > Graphs & Plots), which inom have displayed below.

The graph below compares the extremist score for dock and women and igen highlights the differences between genders.

Advantages of Non-Parametric Statistics.

This fryst vatten a låda Plot with scatter and a violin Plot.

Ho: There fryst vatten no difference in the extremism score of males and females.

Ha: There fryst vatten a difference in the extremism score of males and females.

This fryst vatten the same Hypothesis as above.

To run a kraftig T-Test you will need to install the following Modules:

Walrus: This module provides you with a series of kraftig tests that can be used when the normality assumptions are not meet.

Robust T-Test variables required

Here we use the same variables as in the test above.

  • Gender

  • Extremism_score_Scaled

Robust T-Test Assumptions

  1. Independence: Your observations in each sample should be independent

  2. Random Sampling: Your uppgifter should be a random sample of the mål population

Robust T-Test: Step-by-Step Guide 

Navigate to Analyses > Walrus > kraftig Independent Sample T-Test

Now drag & drop your two variables into the correct place.

Select your Statistics & Plot