Any time you seek further information about one of these concepts, simply click on the link to go directly to that term in the glossary. Interval variables, the third level of measurement , have all the properties of ordinal variables , but in addition have the property that equal differences between measures represent equal differences in the values of the variable . A variable must be at least interval to be able to compute a meaningful average. Each Main Menu Option from the represents a self-instructional lesson that can be chosen and used to learn, present, practice or review statistics concepts and skills. Use the arrow keys or mouse to select the desired lesson.
Lessons typically have a number of sections also accessed from menu.
The browser interface is quite intuitive and consistent with typical graphical user interface standards. The mean refers to the average. It is one of the most useful measures of central tendency. The mean is calculated by finding the sum of the measures and dividing by the number of measures. Measurement is a systematic process of assigning names, labels, or numbers to the different values of a variable .