Introduction

Frequency polygons are analogous to line graphs, and just as line graphs make continuous data visually easy to interpret, so too do frequency polygons.

To construct a frequency polygon, first examine the data and decide on the number of intervals, or class intervals, to use on the x-axis and y-axis. After choosing the appropriate ranges, begin plotting the data points. After all the points are plotted, draw line segments to connect them.

Example of how a frequency polygon is made from a histogram

Time Series graphs are very similar to line graphs. They display data over a period of time. Similarly to other graphs, we can use these to graph one set of data or we can compare data sets on one graph.

To construct a time series graph, we must look at both pieces of our paired data set. We start with a standard Cartesian coordinate system. The horizontal axis is used to plot the date or time increments, and the vertical axis is used to plot the values of the variable that we are measuring. By doing this, we make each point on the graph correspond to a date and a measured quantity. The points on the graph are typically connected by straight lines in the order in which they occur.

example of a time series graph

What You Will Do

Watch this video from The Friendly Statistician about Frequency Polygons:

Watch this video from The Organic Chemistry Tutor about Frequency Polygons:

Watch this video from Dr. Nic's Maths and Stats about time series graphs:

Read about frequency polygons in the following Section in our text:

2.2 Histograms, Frequency Polygons, and Time Series Graphs

What's Next

You will complete a Progress Check about the material so far.