Southern New Hampshire University
MAT-133
Week 2 Notes
Stem and Leaf Display
One simple way to visualize small data sets is a The stem-and-leaf plot is a stem-and-leaf plot.
tool of (EDA) that seeks to reveal essential data features in an intuitiveexploratory data analysis
way. A stem-and-leaf plot is basically a frequency tally, except that we use digits instead of tally
marks. For two-digit or three-digit integer data, the is the tens digit of the data, and the stem leaf
is the ones digit.
A stem-and-leaf plot works well for small samples of integer data with a limited range but
becomes awkward when you have decimal data (e.g., $60.39) or multidigit data (e.g., $3,857). In
such cases, it is necessary to round the data to make the display “work.” Although the stem-and-
leaf plot is rarely seen in presentations of business data, it is a useful tool for a quick tabulation
of small data sets.
Dot Plots
A is another simple graphical display of individual values of numerical data. The basicdot plot n
steps in making a dot plot are to (1) make a scale that covers the data range, (2) mark axis
demarcations and label them, and (3) plot each data value as a dot above the scale at its
approximate location. If more than one data value lies at approximately the same -axis location,X
the dots are piled up vertically.
Dot plots are an attractive tool for data exploration because they are easy to understand. A dot
plot shows by displaying the range of the data. It shows the by revealing wherevariability center
the data values tend to cluster and where the midpoint lies. A dot plot also can reveal the ofshape
the distribution if the sample is large enough.
While they are easy to understand, dot plots have limitations. They don’t reveal very much
information about the data set’s shape when the sample is small, and they become awkward
when the sample is large (what if you have 100 dots at the same point?) or when you have
decimal data.
