In need of a specific statistic test

Hi,

I am looking for a single-tailed, paired, non-parametric statistic test.

Specifically, I have (Xi,Yi) pairs and I want to know whether X is consistently larger than Y, or vica versa, in a significant manner (i want to be able to quantify the significance either way).

Is there such a thing implemented in Matlab? Ranksum and signrank are close to what i need but are both two-tailed.

Thanks!

Shay

Answer 1

[TED MOSBY]

Hi Shay,

The ‘signrank’ function in MATLAB is a two-tailed test by default, but you can specify it to perform a one-tailed test using the ‘tail’ parameter. After setting this parameter, you can test a specific directional hypothesis:

• 'tail', is set to'right': Tests if the median of X - Y is greater than zero (i.e., X is consistently greater than Y).
• 'tail', is set to 'left': Tests if the median of X - Y is less than zero (i.e., Y is consistently greater than X).

I wrote an example of how to use ‘signrank’ for a one-tailed test which you can refer:

% Your data 
X = [...]; % Your X values 
    Y = [...]; % Your Y values 
    % Perform the Wilcoxon signed-rank test (one-tailed) 
    [p, h, stats] = signrank(X, Y, 'tail', 'right'); % Test if X is greater than Y 
    % Alternatively, test if Y is greater than X 
    % [p, h, stats] = signrank(X, Y, 'tail', 'left'); 
    % Display the results 
    fprintf('p-value: %f\n', p); 
    fprintf('Test statistic: %f\n', stats.signedrank); 
    fprintf('Hypothesis result (1 if rejected, 0 if not): %d\n', h); 

Here is the documentation for the ‘signrank’ function:

www.mathworks.com/help/stats/signrank.html?searchHighlight=signrank&s_tid=srchtitle_support_results_1_signrank

Hope this helps!