The following tests can be used with all types of "scale"data. These include dependent variables measured on approximately interval, interval, or ratio scales of measurement. Which test you select is determined by the number of samples and whether you are testing a hypothesis about group differences or the association between independent and dependent variables. If you are testing a hypothesis about group differences, you also must consider whether the groups/samples are independent or dependent and how many samples you have in the study design. Some parametric statistics also permit analysis of more than one independent variable.