How can I report the results obtained from the kruskal wallis test in the boxplots? How to highlight the significance?

I performed the kruskal wallis test on 8 samples. At the output I have the p value, SS, MS and I also made the pair wais among the various combinations. How can I report the results obtained from the kruskal wallis test in the boxplots? How to highlight the significance?

Answer 1

[Yash]

Hi Ilaria,

As I can understand, you are interested in highlighting the results obtained from the kruskal wallis test. To achieve this, I suggest you follow the below steps:

1. Use the "boxplot" function to to cretate boxplots for your 8 samples. This will give you a visual representation of the data.
2. To highlight the significance levels on the boxplots, you can use symbols such as asterisks. Determine the significance level threshold (e.g., p < 0.05) and add the corresponding symbols to the boxplots for the groups that are significantly different.
3. In the figure caption or the accompanying text, report the results of the Kruskal-Wallis test. Include the p-value, SS (Sum of Squares), MS (Mean Squares), and any relevant pairwise comparisons you made.

Kindly have a look at the below example for your reference.

% Perform Kruskal-Wallis test
p = kruskalwallis([sample1, sample2, sample3, sample4, sample5, sample6, sample7, sample8]);

% Generate boxplots
figure;
boxplot([sample1, sample2, sample3, sample4, sample5, sample6, sample7, sample8]);
title('Boxplots of the Samples');
ylabel('Values');

% Add significance indicators
if p < 0.05
  % Add asterisk to indicate significance
    hold on;
    significance_groups = {'Group1', 'Group2', 'Group3', 'Group4'};
    significance_positions = [1, 2, 3, 4];
    plot(significance_positions, max(ylim) * ones(size(significance_positions)), '*', 'MarkerSize', 10);
    text(significance_positions, max(ylim) * ones(size(significance_positions)), significance_groups, 'VerticalAlignment', 'bottom', 'HorizontalAlignment', 'center');
    hold off;
end
% Include test results in the figure caption or accompanying text
disp(['Kruskal-Wallis test p-value: ', num2str(p)]);

I hope this helps you address the issue.