the statistically meaningful display of analog data
DESCRIPTION
The Statistically Meaningful Display of Analog Data. Robert A. Warner, MD Laboratory of Logic and Experimental Philosophy Simon Fraser University Vancouver, BC, Canada. Interpreting Analog Displays. Do any parts of the display differ from a reference standard? - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: The Statistically Meaningful Display of Analog Data](https://reader034.vdocuments.site/reader034/viewer/2022051516/56813298550346895d99320e/html5/thumbnails/1.jpg)
The Statistically Meaningful
Display of Analog Data
Robert A. Warner, MD
Laboratory of Logic and Experimental Philosophy
Simon Fraser University
Vancouver, BC, Canada
![Page 2: The Statistically Meaningful Display of Analog Data](https://reader034.vdocuments.site/reader034/viewer/2022051516/56813298550346895d99320e/html5/thumbnails/2.jpg)
Interpreting Analog Displays
• Do any parts of the display differ from a reference standard?
• Are the differences genuine or merely variants of normal?
![Page 3: The Statistically Meaningful Display of Analog Data](https://reader034.vdocuments.site/reader034/viewer/2022051516/56813298550346895d99320e/html5/thumbnails/3.jpg)
An Individual Value vs. A Reference Population
PopulationMean
A
Individ.Value
A
Individ.Value
B
PopulationMean
B
Measurement Units
1.0SD
1.0SD
![Page 4: The Statistically Meaningful Display of Analog Data](https://reader034.vdocuments.site/reader034/viewer/2022051516/56813298550346895d99320e/html5/thumbnails/4.jpg)
Standard (Z) Scores
(Individual Value – Population Mean)
Population S.D.
• Positive Z score: individual value>mean• Negative Z score: individual value<mean• Differences are in S.D. of the population
![Page 5: The Statistically Meaningful Display of Analog Data](https://reader034.vdocuments.site/reader034/viewer/2022051516/56813298550346895d99320e/html5/thumbnails/5.jpg)
Advantages of Z Scores
• All parameters are on the same scale (the S.D. of the population)
• No compression at the extremes of a distribution (unlike percentiles)
• Can use demographically specific normal reference populations
• Directly translatable to P values
![Page 6: The Statistically Meaningful Display of Analog Data](https://reader034.vdocuments.site/reader034/viewer/2022051516/56813298550346895d99320e/html5/thumbnails/6.jpg)
Z Scores, P Values & Coding
Z Score P Value B&W Code
>3.08 0.001
>2.33 0.01
>1.65 0.05
-1.64 to 1.64 NS
<-1.65 0.05
<2.33 0.01
<3.08 0.001
![Page 7: The Statistically Meaningful Display of Analog Data](https://reader034.vdocuments.site/reader034/viewer/2022051516/56813298550346895d99320e/html5/thumbnails/7.jpg)
Colors On the Tracing Refer To Amplitudes Colors Above the Tracing Refer to Durations
Analog ECG Display
COLOR CODES Z Score P Value
3.08 .001 2.33 .01 1.65 .05
-1.64 to 1.64 NS -1.65 .05 -2.33 .01 -3.08 .001
PR = 230Msec.
Q = 34Msec.
S = 0Msec.
![Page 8: The Statistically Meaningful Display of Analog Data](https://reader034.vdocuments.site/reader034/viewer/2022051516/56813298550346895d99320e/html5/thumbnails/8.jpg)
Colored Z Score Matrix
To Accompany a Standard ECG
Diagnosis: Acute Inferior MI
Q Q R R S S ST T
Lead Amp Dur Amp Dur Amp Dur Amp Amp
I # # # # # # # #
II # # # # # # # #
III # # # # # # # #
aVR # # # # # # # #
aVL # # # # # # # #
aVF # # # # # # # #
V1 # # # # # # # #
V2 # # # # # # # #
V3 # # # # # # # #
V4 # # # # # # # #
V5 # # # # # # # #
V6 # # # # # # # #
![Page 9: The Statistically Meaningful Display of Analog Data](https://reader034.vdocuments.site/reader034/viewer/2022051516/56813298550346895d99320e/html5/thumbnails/9.jpg)
B&W Z Score MatrixTo Accompany a Standard ECG
Diagnosis: Acute Inferior MI
Q Q R R S S ST T
Lead Amp Dur Amp Dur Amp Dur Amp Amp
I # # # # # #
II # # # #
III # # # #
aVR # # # # # # # #
aVL # # # # # #
aVF # # # #
V1 # # # # # # # #
V2 # # # # # # # #
V3 # # # # # # # #
V4 # # # # # # # #
V5 # # # # #
V6 # # # # #
![Page 10: The Statistically Meaningful Display of Analog Data](https://reader034.vdocuments.site/reader034/viewer/2022051516/56813298550346895d99320e/html5/thumbnails/10.jpg)
Validation of the Z Score Method
• Compared abilities of Z scores vs. 2 widely-used commercial ECG algorithms to detect prior inferior and anterior MI
• 1138 patients (mean age 53, 426 females), 497 cath-proven normals, 366 prior inferior MI, 275 prior anterior MI
• Used Z scores of Q waves in aVF and initial R waves in V2
• The commercial algorithms use voltages, not Z scores.
![Page 11: The Statistically Meaningful Display of Analog Data](https://reader034.vdocuments.site/reader034/viewer/2022051516/56813298550346895d99320e/html5/thumbnails/11.jpg)
Inferior MIZ Scores vs. AlgorithmsSensitivities @ 95% Specificity
0
1020
3040
5060
7080
90100
Z Score Alg. 1 Alg. 2
• Z vs. Algorithm 1
Chi Square = 43.9
P<0.0000001
• Z vs. Algorithm 2
Chi Square = 20.3
P<0.000001
![Page 12: The Statistically Meaningful Display of Analog Data](https://reader034.vdocuments.site/reader034/viewer/2022051516/56813298550346895d99320e/html5/thumbnails/12.jpg)
Anterior MIZ Scores vs. AlgorithmsSensitivities @ 95% Specificity
0
1020
3040
5060
7080
90100
Z Score Alg. 1 Alg. 2
• Z vs. Algorithm 1
Chi Square = 24.1
P<0.000001
• Z vs. Algorithm 2
Chi Square = 9.2
P<0.002
![Page 13: The Statistically Meaningful Display of Analog Data](https://reader034.vdocuments.site/reader034/viewer/2022051516/56813298550346895d99320e/html5/thumbnails/13.jpg)
Z Scores in Long Recordings
• Objective and quantifiable comparisons to normal reference and baseline data
• Statistically meaningful results• Cost-Effective
– Rapid interpretation– Doesn’t require highly trained personnel
• Full disclosure of data• Permits multiparameter recordings
![Page 14: The Statistically Meaningful Display of Analog Data](https://reader034.vdocuments.site/reader034/viewer/2022051516/56813298550346895d99320e/html5/thumbnails/14.jpg)
Rapid Review of Data
10 11 12 1 2 3 4 5 6 7 8 9AM AM AM PM PM PM PM PM PM PM PM PM
10 11 12 1 2 3 4 5 6 7 8 9PM PM PM AM AM AM AM AM AM AM AM AM
6PM
7:00PM
PM PM6:20 6:25
PM
6:30 6:45
PM6:05 6:10 6:15PM
PM6:35PM
6:40PM PM
6:50PM
6:55PM
Ischemia Monitoring – 24 Hour DisplayMarch 4 to March 5, 2010
Colors = Maximum ST Segment Displacement
Ischemia Monitoring – 1 Hour DisplayMarch, 2010 – 6:00 to 7:00 PM
![Page 15: The Statistically Meaningful Display of Analog Data](https://reader034.vdocuments.site/reader034/viewer/2022051516/56813298550346895d99320e/html5/thumbnails/15.jpg)
Multiparameter Monitoring
• Maximizes the types of useful data provided
• Concordant orthogonal parameters increase the accuracy of diagnosis
• Parameters measured in different units are hard to display simultaneously and to interpret
![Page 16: The Statistically Meaningful Display of Analog Data](https://reader034.vdocuments.site/reader034/viewer/2022051516/56813298550346895d99320e/html5/thumbnails/16.jpg)
Importance of Similar Scales
0.00
5.00
10.00
15.00
20.00
25.00
1 5 9
13
17
21
25
29
33
37
41
45
49
53
57
61
65
69
73
77
81
85
89
93
97
-2.50
-2.00
-1.50
-1.00
-0.50
0.00
0.50
1.00
1.50
2.00
2.50
1 5 9
13
17
21
25
29
33
37
41
45
49
53
57
61
65
69
73
77
81
85
89
93
97
Raw Data A
Raw Data B
Z Scores AZ Scores B
![Page 17: The Statistically Meaningful Display of Analog Data](https://reader034.vdocuments.site/reader034/viewer/2022051516/56813298550346895d99320e/html5/thumbnails/17.jpg)
Z Scores in Acute Anterior MI
-30.00
-20.00
-10.00
0.00
10.00
20.00
30.00
Time
Z S
core
ST_V2
ST_aVF
S4 Conf
S3 Conf
HEARTRATE
MI Onset
![Page 18: The Statistically Meaningful Display of Analog Data](https://reader034.vdocuments.site/reader034/viewer/2022051516/56813298550346895d99320e/html5/thumbnails/18.jpg)
Z Scores in Acute Anterior MI
COLOR CODES Z Score P Value
3.08 .001 2.33 .01 1.65 .05
-1.64 to 1.64 NS -1.65 .05 -2.33 .01 -3.08 .001
MI Onset
![Page 19: The Statistically Meaningful Display of Analog Data](https://reader034.vdocuments.site/reader034/viewer/2022051516/56813298550346895d99320e/html5/thumbnails/19.jpg)
Exploratory AnalysisWhat can Z scores teach us?
Absolute Z scores of 159 known normals vs. 103 known healed anterior MI’s. Which parts of which leads discriminate the best?
![Page 20: The Statistically Meaningful Display of Analog Data](https://reader034.vdocuments.site/reader034/viewer/2022051516/56813298550346895d99320e/html5/thumbnails/20.jpg)
Some Uses of Z Scores• Medical practice and research• Physical, biological and behavioral science• Engineering, industrial processes and quality
control• Assessing the performance of mechanical
and electrical equipment • Economics, finance and investing• Teaching the interpretation of analog displays• Biofeedback
![Page 21: The Statistically Meaningful Display of Analog Data](https://reader034.vdocuments.site/reader034/viewer/2022051516/56813298550346895d99320e/html5/thumbnails/21.jpg)
Thank you!