ABSTRACT
This chapter introduces a few statistical definitions. Qualitative variables describe a quality or characteristic on each experimental unit, while quantitative variables measure a numerical quantity or amount in each experimental unit. Qualitative variables produce categorical data, while quantitative variables produce both discrete and continuous data. The first thing to keep in mind is that the results are worthless if people do not give the reader an estimate of their errors. Random errors affect precision and can be caused by both the experimenter and/or the equipment and can be estimated and minimized. Perhaps the simplest measure of the center of a data-set is the sample median. The sample median is the value that most nearly lies in the middle of the sample. It is the data value that splits the ordered data into two equal halves. The mode can be defined as the most common value that occurs in a discrete data-set.
