Error in paired t-test between corresponding elements.

I am trying to perform paired t-test between corresponding elements of group1 and group2. It should provide non-NaN p-values for each corresponding pair but it is providing NAN values. Please help to resolve the error. Below is my code.

% Define the data for two groups
group1 = [10, 15, 20, 25, 30];
group2 = [12, 18, 22, 28, 32];

% Initialize array to store p-values
p_values = zeros(size(group1));

% Check if the sizes of the two groups are the same
if numel(group1) ~= numel(group2)
    error('The sizes of the two groups must be the same.');
end

% Perform paired t-test for each pair of corresponding elements
for i = 1:numel(group1)
    fprintf('Performing t-test for Node %d...\n', i);
    
    % Perform paired t-test for the current pair
    [~, p_values(i)] = ttest(group1(i), group2(i));
end

% Display the p-values for each corresponding pair
for i = 1:numel(group1)
    fprintf('Node %d: p-value = %f\n', i, p_values(i));
end

[VBBV]

The input data for samples need to be vectors when using ttest or ttest2 functions to evaluate the p-values

Answer 1

[VBBV]

% Define the data for two groups
group1 = [10, 15, 20, 25, 30];
group2 = [12, 18, 22, 28, 32];

% Initialize array to store p-values
p_values = zeros(size(group1));

% Check if the sizes of the two groups are the same
if numel(group1) ~= numel(group2)
    error('The sizes of the two groups must be the same.');
end

% Perform paired t-test for each pair of corresponding elements
for i = 1:numel(group1)
    fprintf('Performing t-test for Node %d...\n', i);
    
    % Perform paired t-test for the current pair
    [~, p_values(i)] = ttest(group1, group2(i)); % use a vector for paired comparison test
end

Performing t-test for Node 1...
Performing t-test for Node 2...
Performing t-test for Node 3...
Performing t-test for Node 4...
Performing t-test for Node 5...

% Display the p-values for each corresponding pair
for i = 1:numel(group1)
    fprintf('Node %d: p-value = %f\n', i, p_values(i));
end

Node 1: p-value = 0.086418
Node 2: p-value = 0.601832
Node 3: p-value = 0.601832
Node 4: p-value = 0.086418
Node 5: p-value = 0.027426

p_values

p_values = 1x5

0.0864 0.6018 0.6018 0.0864 0.0274

[Haya Ali]

Thank you so much. May I ask what have you altered in the code? Since for the following data I have performed the altered code provided by you and it doesnt seems to give right results because element 3 in both groups are same so p value shouldn't be 0.02.

close all; clear all; clc;
% Define the data for the paired samples
group1 = [19, 19, 20, 18, 19, 19, 20, 21, 20, 16, 18, 21, 20, 18, 18, 20, 20, 18, 20, 19, 22, 21, 19];
group2 = [19, 16, 20, 21, 19, 19, 18, 18, 17, 15, 21, 21, 20, 19, 20, 22, 20, 16, 20, 15, 17, 19, 20];

[VBBV]

% Define the data for two groups
% group1 = [10, 15, 20, 25, 30];
% group2 = [12, 18, 22, 28, 32];

close all; clear all; clc;
% Define the data for the paired samples
group1 = [19, 19, 20, 18, 19, 19, 20, 21, 20, 16, 18, 21, 20, 18, 18, 20, 20, 18, 20, 19, 22, 21, 19];
group2 = [19, 16, 20, 21, 19, 19, 18, 18, 17, 15, 21, 21, 20, 19, 20, 22, 20, 16, 20, 15, 17, 19, 20];


% Initialize array to store p-values
p_values = zeros(size(group1));

% Check if the sizes of the two groups are the same
if numel(group1) ~= numel(group2)
    error('The sizes of the two groups must be the same.');
end

% Perform paired t-test for each pair of corresponding elements
for i = 1:numel(group1)
    fprintf('Performing t-test for Node %d...\n', i);
    
    % Perform paired t-test for the current pair
    [~, p_values(i)] = ttest2(group1, group2(i)); % use a vector for paired comparison test
end

Performing t-test for Node 1...
Performing t-test for Node 2...
Performing t-test for Node 3...
Performing t-test for Node 4...
Performing t-test for Node 5...
Performing t-test for Node 6...
Performing t-test for Node 7...
Performing t-test for Node 8...
Performing t-test for Node 9...
Performing t-test for Node 10...
Performing t-test for Node 11...
Performing t-test for Node 12...
Performing t-test for Node 13...
Performing t-test for Node 14...
Performing t-test for Node 15...
Performing t-test for Node 16...
Performing t-test for Node 17...
Performing t-test for Node 18...
Performing t-test for Node 19...
Performing t-test for Node 20...
Performing t-test for Node 21...
Performing t-test for Node 22...
Performing t-test for Node 23...

% Display the p-values for each corresponding pair
for i = 1:numel(group1)
    fprintf('Node %d: p-value = %f\n', i, p_values(i));
end

Node 1: p-value = 0.801068
Node 2: p-value = 0.022479
Node 3: p-value = 0.637238
Node 4: p-value = 0.238596
Node 5: p-value = 0.801068
Node 6: p-value = 0.801068
Node 7: p-value = 0.333778
Node 8: p-value = 0.333778
Node 9: p-value = 0.099202
Node 10: p-value = 0.004252
Node 11: p-value = 0.238596
Node 12: p-value = 0.238596
Node 13: p-value = 0.637238
Node 14: p-value = 0.801068
Node 15: p-value = 0.637238
Node 16: p-value = 0.064717
Node 17: p-value = 0.637238
Node 18: p-value = 0.022479
Node 19: p-value = 0.637238
Node 20: p-value = 0.004252
Node 21: p-value = 0.099202
Node 22: p-value = 0.801068
Node 23: p-value = 0.637238

p_values

p_values = 1x23

0.8011 0.0225 0.6372 0.2386 0.8011 0.8011 0.3338 0.3338 0.0992 0.0043 0.2386 0.2386 0.6372 0.8011 0.6372 0.0647 0.6372 0.0225 0.6372 0.0043 0.0992 0.8011 0.6372

[VBBV]

Hi @Haya Ali, for two sample t-test, check the ttest2 function instead of regular ttest

[Haya Ali]

Thank you!