Bubble Chart
A bubble chart is a variation of a
scatter chart in which the data points
are replaced with bubbles, and an additional dimension of the data is
represented in the size of the bubbles. Just like a scatter chart, a bubble
chart does not use a category axis — both horizontal and vertical axes are
value axes. In addition to the x values and y values that are plotted in a
scatter chart, a bubble chart plots x values, y values, and z (size) values.
You
can use a bubble chart instead of a scatter chart if your data has three data
series that each contain a set of values. The sizes of the bubbles are
determined by the values in the third data series.
Bubble charts are often used to
present financial data. Different bubble sizes are useful to visually emphasize
specific values.
To create a bubble chart, arrange
your data in rows or columns on a worksheet so that x values are listed in the
first row or column and corresponding y values and bubble size (z) values are
listed in adjacent rows or columns. For example, organize your worksheet data
as shown in the following picture.
In this bubble chart, the number of
products is displayed along the horizontal axis, the sales amounts are
displayed along the vertical axis, and the market share percentages are
represented by the size of the bubbles.
Consider using a bubble chart when
your data includes the following:
- Three values per data point Three values are required for each bubble. These values can be in rows or columns on the worksheet, but they must be in the following order: x value, y value, and then z value.
- Multiple data series Plotting multiple data series in a bubble chart (multiple bubble series) is similar to plotting multiple data series in a scatter chart (multiple scatter series). Scatter charts use sets of x values and y values, but bubble charts use sets of x values, y values, and z values.
When you create a bubble chart, you
can choose one of the following bubble chart subtypes.
- Bubble or bubble with 3-D effect Both bubble chart types compare sets of three values instead of two. The third value determines the size of the bubble marker. You can choose to display bubbles in 2-D format or with a 3-D effect.
Radar Chart
A radar chart graphically shows
the size of the gaps among five to ten organizational performance areas. The
chart displays the important categories of performance and makes visible
concentrations of strengths and weaknesses.
A radar chart shows how a team
has evaluated a number of organizational performance areas. It is therefore
essential that the initial evaluation include varied perspectives to provide an
overall
realistic and useful picture of
performance.
Create
categories. Use
headers from an affinity diagram or brainstorm major categories of
organizational performance to be
plotted. A radar chart can normally include five to ten categories.
Standardize
performance definitions. Have all evaluators agree to use standardized
definitions of both full
performance and non-performance in each category so that ratings are
performed consistently. Define
the scoring range (e.g., 0 to 5 with 5 being full performance).
Rate each
performance category.
Each evaluator rates each category individually, and the
team then develops an average or
consensus score for each category. Alternatively, the team as a
whole may initially develop an
average or consensus score for each category.
Construct the
chart.
1. Draw a large circle and insert
as many spokes or radii as there are performance categories.
2. Around the perimeter of the
circle, label each spoke with the title of a performance
category.
3. Subdivide each spoke into the
number of increments established in the rating scale. Label
the center of the circle where
spokes join as 0 (no performance) and place the highest rating
number (full or exceptional
performance) at the end of the spoke at the outer ring.
Plot the ratings. For each
performance category, plot on the chart the associated rating. Then
connect the plotted points on all
the spokes. Highlight the enclosed central shape as necessary for
ease in viewing.
Interpret and
use the results.
The resulting radar chart will graphically show areas of relative strength and
relative weakness, as well as depicting general overall performance
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