Displaying and describing data

One of the first things we do in statistics is try to understand sets of data. This involves plotting the data in different ways and summarizing what we see with measures of center (like mean and median) and measures of spread (like range and standard deviation). This topic focuses on concepts that are often referred to as "descriptive statistics".

Statistics gives us the tools to effectively answer questions using data. So the first step in actually doing statistics is to form a question! This tutorial looks at what type of questions we deal with in statistics.

Stem-and-leaf plots are another way to plot numerical data. They combine the best features of dot plots and histograms. Turn your head sideways and look at a stem-and-leaf plot and you'll see what we mean.

Line graphs show change over time in a numerical variable.

Standard deviation tells us how far away from the mean each data point typically is in a set of numbers. How we calculate standard deviation depends on whether the data represents an entire population or came from a sample. This tutorial focuses on the data that represents an entire population.