Independent T-Test

The Independent t-test is a parametric test for comparing the means of two groups.

Assumptions
The assumptions of this test are as follows:
 * 1) The data must be normally distributed.
 * 2) The variables must be at least at the interval level.

Non-Parametric Equivalent
The non-parametric equivalent of this test is the Mann-Whitney test.

Example
Consider you have a group of people who exercise every day (Group 1) and a group of people who do not (Group 2). You conduct a study to see how long it takes each person to run 1 mile. An Independent T-Test could be conducted to see if the average times of the two groups differ, deomonstrating whether or not Group 2, who exercise daily, can run 1 mile in less time than Group 2.

In SPSS
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Writing up
An independent-samples t-test was conducted to compare memory for words in sugar and no sugar conditions. There was a significant difference in the scores for sugar (M=4.2, SD=1.3) and no sugar (M=2.2, SD=0.84) conditions; t (8)=2.89, p = 0.20. These results suggest that sugar really does have an effect on memory for words. Specifically, our results suggest that when humans consume sugar, their memory for words increases.