Wonder_Woman wrote on Oct 4
th, 2007 at 10:50pm:
Kim English has done studies and I have attended several of her presentations (I have spoken to her too). One of her studies was from 1996-2001 'English, Pullen & Jones' Percentage accuracy as follows:
Diagnostic Accuracy Assessment Tool
Acute Appendicitis CT 95%
Brain Tumor91%
Carotid Artery Disease 91%
Acute Appendicieis US 91%
Breast Cancer US 90%
Deception - Polygraph 88%
Multiple Sclerosis 83%
Xray 80%
Depression 74%
Also,
Diagnostic Accuracy by Target Condition
Polygraph 88%
MRI 86-87%
Cat Scan 85-86%
Ultra Sound 85%
Xray 82%
CSM 70%
MMPI 67%
Ah, thanks for bringing it back to my expertise...
As I pointed out in prior posts and to Kim several years ago, accuracy in diagnostic testing has 5 statistics that are needed to measure it. So these comparisons are incomplete and do not show the whole picture.
Once again, these are the five things needed to assess "accuracy":
1. Sensitivity, which is the probability that the test is positive given that the person has the underlying condition.
2. Specificity, which is the probability that the test is negative given that the person does not have the underlying condition.
3. Positive predictive value (PPV), which is the probability that the person has the condition given that the test is positive. Its complement is the false positive rate.
4. Negative predictive value (NPV), which is the probability that the person does not have the condition given that the test is negative. Its complement is the false negative rate.
5. Base rate, which is the prevalence of the condition in the population or the probability that you've got someone with the condition. This is also the "chance" of just guessing correctly whether the person has the condition or not.
Sensitive and specificity are usually measured in lab studies.
The base rate, at least for diseases, is estimated from medical records.
PPV and NPV are both functions of sensitivity, specificity, and the base rate. These measure how the diagnostic tests perform when the true status of the underlying condition is unknown, which is the case in screening applications.
Basically, they are a measure of how well the test performs when compared against a gold standard. Any PPV or NPV less than 90% has no usefulness in my opinion.
Additionally, when the base rate is low (deception in employment screening), your PPV goes down and your false positive rate goes up. Conversely, when your base rate is high (deception in sex offending), your NPV goes down and your false negative rate goes up.
And without showing PPV, NPV, and base rates of the conditions those test measure, the numbers above are incredibly misleading and completely without context...
Additionally, unlike like the polygraph, all of those medical listed tests can be run sequentially or in concert to reduce the probability of error. Once a person has been polygraphed, because of the nature of the test there is a high likelihood of prior tests affecting future tests...
Wonder_Woman wrote on Oct 4
th, 2007 at 10:50pm:
Also, Just because I say FU doesn't mean I am intellectually weak. It means FU
I'll leave it up to others to determine the strength of your argument.
Wonder_Woman wrote on Oct 4
th, 2007 at 10:50pm:
I would believe that Kim English's study used the CQT. (Kim English, Director, Office of Research & Statistics - a true beleiver) But, hey, since you know her so well, why don't you ask.
No need to ask, her study does use it...