Introduction: Numerical Summaries of Data

Learning Objectives

  • Calculate the mean, median, and mode of a set of data
  • Calculate the range of a data set, and recognize it’s limitations in fully describing the behavior of a data set
  • Calculate the standard deviation for a data set, and determine it’s units
  • Identify the difference between population variance and sample variance
  • Identify the quartiles for a data set, and the calculations used to define them
  • Identify the parts of a five number summary for a set of data, and create a box plot using it

It is often desirable to use a few numbers to summarize a data set. One important aspect of a set of data is where its center is located. In this lesson, measures of central tendency are discussed first. A second aspect of a distribution is how spread out it is. In other words, how much the data in the distribution vary from one another. The second section of this lesson describes measures of variability.