MASH : Maths and Stats Help

Independent Samples t-Test, using Jamovi

Introduction

An independent-samples t-test compares the means between two unrelated groups, such as comparing the difference between class A and class B, another very common example would be used to compare a binary gender difference.

If you have three or more groups consider using a One-Way Between-Subjects ANOVA

An independent-samples t-test is considered a parametric test and is only suitable for parametric data. To check if your data is parametric, please read our dedicated guide: Parametric or Not Guide (PDF)

If your data is non-parametric you could consider using a Mann-Whitney U-Test.

Test Procedure

1. To carry out an independent t-test, you'll need to identify two columns of data to use. One with for the data independent (or grouping) variable, and another for the dependent (or test) data.

2. Select the "T-Tests" option, drop down the menu and select "Independent Samples T-Test":

3. The Independent Samples T-Tests options will open. Using the arrow button, move the dependent variable across to the "Dependent Variables" box and the independent variable into the "Grouping Variable" box. Look though the options on this view for additional information you may want, here we have selected the addition of "Descriptives" to get the minimal data for the write up. Your results will appear to the right of the options box, and will update as you tick or untick options.

Results

Jamovi produces the results as you add variables and tick options. If you have results that you don't need or find you have not selected all that you want, you can come back to the menu at any point to change your selection. For this t-test, the results are given in two tables; an "Independent Samples T-Test" table and a "Group Descriptives" table, these are produced in APA style formatting.

Group Descriptives

This table shows a selection of descriptive statistics: the sample size of each group (N), the mean of each group (Mean), the median of each group (Median), the standard deviation of each group (SD) and the standard error (SE). Typically the N, Mean and SD or SE are reported.

Independent Samples t-Test

This table shows the specific test results including the t-statistic (Statistic), the degrees of freedom (df), the p-value (p), the difference between the group means (Mean difference) and the 95% Confidence Intervals (95% Confidence Interval, lower and upper).