Guides to graphs and charts
Which chart fits your data, how to read the one in front of you, and the mistakes that cost points. Every example chart is drawn from a table you can paste into a free maker.
Types of graphs and when to use each one
The right type of graph depends on the question your data has to answer: comparing groups, showing change over time, showing parts of a whole, showing how values are spread out, or showing how two variables relate. Bar graphs, line graphs, pie charts, histograms, box plots and scatter plots each answer one of those questions well and the others badly.
Read the guideHistogram vs bar graph: what's the difference?
A histogram shows how numbers are spread across ranges, such as test scores grouped into 10-point bins. A bar graph compares counts or values for separate categories, such as letter grades or favorite subjects. Both are made of bars, but they answer different questions, and a teacher grading a stats assignment will notice which one you picked.
Read the guideBar graph vs line graph: when to use each
Use a bar graph to compare separate categories and a line graph to show change across continuous time. That one rule settles most bar graph vs line graph choices, and the exceptions, like a handful of time points or two groups side by side, are covered below.
Read the guideHow to read a histogram
A histogram shows how many values in a dataset fall into each range, called a bin. To read one, check the axes and bins first, then the counts, peak, center and spread, and finally the overall shape, which tells you whether the mean or the median is the better summary.
Read the guide