ABSTRACT
The key initial consideration in determining which statistics to use in a research study is the scale on which the variables of interest are measured. Descriptive statistics provide information about individual variables being studied, inferential statistics provide information about relationships between variables. Although there are many types of scales, the most important distinction is whether the scale provides at least interval-level information. Categorical and ordinal scales are the two types that provide less information compared to interval or better scales. Categorical scales, sometimes called nominal scales, are used to describe variables that only provide information about the category or group in which a unit is contained. The scales providing the most information for school psychology research are interval-level or better. The intervals on these scales are equally spaced so the quantitative difference between numbers has meaning.
