CHAPTER20 Measures of Center and Spread
In This Chapter
- Identifying mean, median,
and mode - Using percentiles and
quartiles - Measuring the spread of
data
When researchers have a question, they perform lots of
experiments or pose their question to many people and then
they record all the results or responses. All that data can
provide lots of information, but there may be so much data
that it’s difficult to make sense of it. It can turn into just a
flood of numbers.
To make sense of information, you often need ways to
summarize it and describe the patterns in it. Statistics are
numbers that summarize collections of data or information.
They help you to draw conclusions about the data.
In this chapter, you’ll look at the statistics that give you the
most important information. You’ll find the measures of
center, the numbers that tell you about the average or typical
value. You’ll also find the numbers that divide the data into
groups, allowing you to compare different results. For the big
picture, you’ll talk about how spread out the data are, using a
few simple numbers (and one not-so-simple one).