Stem and Leaf Plots are a great way to organize lists of numbers in an appealing way. They take long lists of data points and organizing them. But, as with any plot or graph, some context is needed. A Key (or Legend) is used with a stem and leaf plot to give this context.
A stem and leaf plot key shows what a typical entry represents. If applicable, it will also show the units of measurement (percent, feet, inches, etc.). A key is also how you denote if the entries include decimal points.
A proper stem and leaf plot should ALWAYS have a key. The bad news is sometimes you must dig a little to find it. Sometimes it won’t be labeled as a “Key,” and sometimes you’ll have to read for clues in a word problem. Worse yet, sometimes a key won’t be included at all, and you’ll have to look at the actual number set to see what a typical entry looks like.
Stem and Leaf Plot Key Examples
- Key: 3 | 2 = 32% – Denotes number and percentage
- Key: 3 | 2 represents 3.2 seconds – Denotes decimal location and units
- Key: 3 | 2 represents 32 meters – Shows number and units
- 3 | 2 is 32 – This is the bare minimum, but is very common. (Note it is not even labeled “Key”)
The most common location for a key is centered under the plot, but there is no “standard” location. Keys can also be placed above, on the side, or mentioned in the context of a word problem.
What a Stem and Leaf Plot Key MUST Have
- It MUST be there!
- A “typical” entry
- Units of measurement
Sometimes you will have to create a stem and leaf plot, either for a homework question or exam. Although most plots are easy to understand, you run the risk of losing points if you do not include these things. Remember, you don’t want to simplify a lot of data into an easy to read format just to confuse someone as to what each data point actually means.
If you have any other questions about these plots or keys, leave a comment below!