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JRCERT Update

Visualization in Data Analysis

However, data can be manipulated in various ways, A
16.5%
so it often is valuable to use more than 1 visualization
32%
technique to give a complete and accurate picture of the
26.5%
information. 16.5%
25%
Pie Charts 32%
A pie chart best communicates data that can be
shown in a simple image to represent parts of a whole. 26.5%
Image Production
Patient Care
It is used to visualize nominal, descriptive categories,
Safety
Procedures
such as demographic information, or ordinal catego- 25%
ries, such as ranked survey data. Pie charts are most
appropriate for displaying data split into 6 categories or
fewer. When there are more categories, it is difficult to
3
ARRT First Attempt Pass Rate
distinguish between the relative sizes of the different Patient Care Image Production
110
sections, and the chart is difficult to interpret. Three- Safety Procedures
First Attempt Pass Rate 100
90
dimensional pie charts also are difficult to interpret as
80
70
they can visually distort information (see Figure 1).
60
Notice how the section showing image production,
50
40
which makes up 25.5% of the entire exam (or 50 out of B 16.5%
30
20
200 total questions), appears as large or larger than the 32%
10
0
Safety section, which makes up 26.5% (or 53 out of 200 2016 26.5%
2015
2013
2014
2012
Year
total questions). This illusion occurs because adding 25% 16.5%
a third dimension distorts the perception of the slices' 32%
relative sizes. Patient Care Student Learning
Outcome Benchmark Score 2.5
ARRT Scores
4 2013-2016
Column Charts 2.7 2.8 2.7 2.7 2.8 2.8 2.7 2.65 2.7 89 26.5%
Learning Outcome Score
3.5
3
A column chart can show changes in categorical data 88 Patient Care Image Production
87
2.5
sets over time, or longitudinally. This long-term analysis Average ARRT Test Scores 86 Safety Procedures 25%
85
2
allows educators to base decisions on trends rather than 84
1.5
83
82
1
data from outliers. The x-axis generally shows indepen- Figure 1. Pie charts showing American Registry of Radiologic
81
0.5
80gists (ARRT) radiography examination sections. The 2-D
dent variables, or variables that the educator can choose Technolo 2013 2014 2015 2016
0
2015
ARRT First Attempt Pass Rate
2010
2013
2014
2011
2012
2016
or control (eg, a year), and the y-axis shows dependent 2009 2008 pie chart (A) depicts the proportion of test questions more accurately Patient Care Image Production
Year
Year
than the 3-D pie chart (B), which distort
Programs the information. Figures
National
110
variables, or the variables that the educator wants to mea- courtesy of the author. State Safety Procedures
sure (eg, ARRT exam scores for each graduating class). It 90
80
Average ARRT Scores vs Average HS Math Scores
is extremely important to review the scale of the y-axis to 70
60
4.5
avoid misrepresenting differences between data sets. For First Attempt Pass Rate 100 ARRT Exam Scores
50
2013-2016
4
40
example, the charts in Figure 2 were created using the illustrate whether students are meeting or exceeding a
30
3.5
ARRT Exam Scores
100
20
3
same data and show average ARRT scores grouped at the benchmark over time, which can help educators make
10
80
0
2.5
national, state, and program levels, which is an excellent decisions about adjusting the target (see Figure 4).
2016
2012
2014
2015
2013
60
2
Year
tool for benchmarking. Scaling inconsistency distorts the Average ARRT Test Scores 40
1.5
1
information and misrepresents the data. Scatter Plot Charts
20
Patient Care Student Learning
0.5
Adding a trend line or a benchmark line to a col- A scatter plot chart shows the relationship between 2
0
Outcome Benchmark Score 2.5
0
2014
2013
2015
2016
0
20
40
60
umn chart can assist with better visualization of 80 100 variables or reveals distribution trends. The scatter plot ARRT Scores
Year
2013-2016
4
State
High School Math Scores
Program
National
Learning Outcome Score
subtle trends, whether they are positive or negative shows a positive relationship between high school math 89
3.5
2.7
2.7
2.8
2.8
2.7
2.65
2.7
2.7
2.8
88
3
(see Figure 3). The addition of a benchmark line can grades and higher ARRT average scores (see Figure 5). Average ARRT Test Scores 87
2.5
86
2
85
84
1.5
82
1
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80 RADIOLOGIC TECHNOLOGY, September/October 2017, Volume 89, Number 1 83
0.5
0 80 2013 2014 2015 2016
2016 2015 2014 2013 2012 2011 2010 2009 2008
Reprinted with permission from the American Society of Radiologic Technologists for educational purposes. ©2019. All rights reserved. Year
Year
National Program State
Average ARRT Scores vs Average HS Math Scores
4.5 ARRT Exam Scores
4 100 2013-2016
ARRT Exam Scores 2.5 3 2 Average ARRT Test Scores 80
3.5
60
1.5
40
0.5 1 20
0 0 2013 2014 2015 2016
0 20 40 60 80 100 Year
High School Math Scores National Program State