SPSS Tutorial: Independent samples t-test



The independent t-test, also called the two sample t-test or student's t-test, is an inferential (as opposed to a descriptive) statistical test that determines whether there is a statistically significant difference between the means in two unrelated (read: independent) groups.

Independent sample t-test formula

Two formulae are often used:

1: Averaged standard deviations (not used in SPSS)







2: Pooled standard deviations (used in SPSS)








Assumptions

1: Your dependent variable should be measured on a continuous scale (i.e., it is measured at the interval or ratio level).

2: Your independent variable should consist of two categorical, independent groups.

3: You should have independence of observations, which means that there is no relationship between the observations in each group or between the groups themselves.

4: There should be no significant outliers.

5: Your dependent variable should be approximately normally distributed for each group of the independent variable.

6: There needs to be homogeneity of variances.

SPSS Guide










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