Transcript TQM Tools Pie Chart

TQM Tools
Pie Chart
What is a “Pie-Chart”?
• A pie chart is a way of summarizing a set of
categorical data or displaying the different values
of a given variable (e.g., percentage distribution).
This type of chart is a circle divided into a series
of segments. Each segment represents a
particular category. The area of each segment is
the same proportion of a circle as the category is
of the total data set.
TQM Tools
Pie Chart
Pie charts usually show the component parts of a
whole. Often you will see a segment of the
drawing separated from the rest of the pie in
order to emphasize an important piece of
information.
TQM Tools
Pie Chart
•
How can you construct a “Pie-Chart”?
A pie chart is constructed by converting the share of each
component into a percentage of 360 degrees.
Example for 2 components each 50%:
-
Draw a circle with your protractor.
Starting from the 12 o'clock position on the circle, measure an
angle of 180 degrees with your protractor. The first component
should make up half of your circle(50%). The other half is for the
second 50%
TQM Tools
Pie Chart
P i e C h a r t E x a mp l e
Component A
Component B
TQM Tools
Pie Chart
If you have to do a ‘pie-chart’ with other
percentages you only have to follow an
easy rule to change from your scale to a
360º scale.
360___________100
x_____________y
where x are the degrees corresponded with
your y amount of percentage
TQM Tools
Pie Chart
The following example chart is based on preliminary results of the
election for the European Parliament in 2004.
Group
Seats
Percent (%)
Central angle (°)
EUL
39
5.3
19.2
PES
200
27.3
98.4
EFA
42
5.7
20.7
EDD
15
2.0
7.4
ELDR
67
9.2
33.0
EPP
276
37.7
135.7
UEN
27
3.7
13.3
Other
66
9.0
32.5
Total
732
99.9*
360.2*
*Because of rounding,
these totals do not add
up to 100 and 360.
TQM Tools
Pie Chart
TQM Tools
Pie Chart
Pie charts are a very useful quality tool
because of its simplicity. You can get a
whole idea only by looking at it once.
On this way, you can detect fast:
- Mean the average of all the data points in
the series (when appropiate).
- Maximum the maximum value (biggest
slice) in the series.
TQM Tools
Pie Chart
- Minimum the minimum value (smallest
slice) in the series.
- Sample Size the number of values (slices)
in the series.
- Range the maximum value minus the
minimum value.
- Standard Deviation Indicates how widely
data is spread around the mean.
TQM Tools
Pie Chart
Example : What type of film do people like the most?
TQM Tools
Pie Chart
In this example, we can see:
- Maximum : COMEDY
- Minimum: SCIENCE- FICTION and
FOREIGN
- Sample Size: 7 slices
- Range: 27% - 8% = 19%
TQM Tools
Pie Chart
As we have explained pie charts can be drawn by
hand, however an easier way to create pie
charts is via computer software. For example
Microsoft Excel, MATLAB…