And what about the assumptions? For the test results to be valid, several assumptions must be met!

1. Normality
The data within the groups should be normally distributed. This can be checked with a quantile quantile plot. Or alternatively:
The residuals should be normally distributed.

2. Homogeneity of Variances
The variance of data in groups should be equal. This can be checked with the Levene's test.

3. Independence
The measurements should be independent, i.e. the measured value of one group should not be influenced by the measured value of another group.

4. Measurement Level
The dependent variable should have a metric scale level.