Chapter 9 – Plots, Graphs, and Pictures
Data should stand out, be clear, have a source, and have little extras.
Categorical data can be laid out using things that divide them into categories and pictures. Precharts
show the percentage of the whole that falls into each category. They are simple and show information
more readily than a table. Bar graphs show percentages/frequencies as well, but they can show two or
three categorical variables at a time. Categories are put horizontally, frequencies are vertical. A third can
be shown by adding another bar. These are not always visually appealing.
Pictograms are like bar graphys, but they use pictures related to the topic of the graph. They are not the
best because the picture can be misinterpreted by our eyes. Fixing this problem makes the graph
Graphs are the best way to represent the relationship between 2 measurements. It also shows how a
measurement variable changes over time.
Line graphs are shown over time. They show trends and relative stability.
Scatter plots are useful for showing the relationship between 2 measurement variables. Each dot
represents one individual unless 2 people have the same result. It is more difficult to read than a line
graph, but it displays more information. It shows outliers and degree of variability for one variable at
each location of the other variable.
The most common mistakes on plots, graphs, and pictures are not labellin