An Introduction to Statistics for Librarians (Part Two):

In Part One of this column, the different types of data were discussed. Understanding the type of data is essential to interpreting them. If the type of data isn’t correctly identified, it’s not possible to answer some fundamental questions accurately. One of these fundamental questions is “what’s the average value?” This is often the building block for more advanced statistical tests. In statistical terms, this question is asking us for the central tendency of the data. The central tendency is a single value that represents the midpoint of the data set. It tells us what is “average” or “normal” in the data set. There are three different ways to measure central tendency: mode, median, and mean. The measure chosen will depend on the type of data and the distribution of that data.