2.2. Common Graphs and Data Plots http://www.ck12.org
information by rounding. Data that has large gaps between values can also make the stem plot hard to create and
less useful when interpreting the data.
Back-to-Back Stem Plots
Stem plots can also be a useful tool for comparing two distributions when placed next to each other or what is
commonly called"back-to-back".
In the previous example we looked at recycling in paper packaging. Here is data from the same countries and their
percentages of recycled material used to manufacture glass packaging.
TABLE2.19: Percentage of the paper packaging used in a country that is recycled.
Country % of Glass
Packaging Recycled
Cyprus 4
United States 21
Poland 27
Greece 34
Portugal 39
Spain 41
Australia 44
Ireland 55
Italy 56
Finland 56
France 59
Estonia 64
New Zealand 72
Netherlands 76
Germany 81
Austria 86
Japan 96
Belgium 98
Sweden 100 ∗In a back-to-back stem plot, one of the distributions simply works off the left side of the stems. In this case, the
spread of the glass distribution is wider, so we will have to add a few extra stems. Even if there is no data in a stem,