Stats PPT 4 Flashcards
What is sensitivity?
How good am I at calling disease when gold standard says it’s there. Test is positive for disease. Abnormal.
What is specificity?
How good am I at calling the absence of disease when gold standard says it isn’t there. Normal. Negative.
What’s a Gold standard?
What you are comparing something to, to determine if it’s valid.
Give two examples of a Gold Standard:
Echo compared to cardiac cath. Vascular to Angio.
How is a true positive different from a false positive?
True positive, my positive result agrees with the gold standard for abnormal, or positive.
False positive, I called positive when the gold standard called negative.
How is a true negative different from a false negative?
True negative, my negative result agrees with the gold standard for negative, or normal.
False negative, I called negative when gold standard called positive.
How is sensitivity different from positive predictive value (PPV)?
Both are about agreeing to abnormal.
PPV: What are the chances I was right about my positive findings, per the gold standard?
What does negative predictive value (NPV) tell you?
Of my studies, what percent were normal (negative) by the gold standard?
Who cares more about PPV, you or your patient?
The patient. The doctor, too.
Why do I, the practitioner, care most about sensitivity?
Sensitivity shows my batting average.
In calculations for sensitivity, etc., what is always in the numerator?
Agreements
Which two values are in the denominator for specificity?
True positives and true negatives.
What is always in the denominator for PPV and NPV?
All my normals or all my abnormals.
What is always in the denominator for overall accuracy?
All of the tests. Add all four boxes.
Are these calculations always about the accuracy of tests?
No. Sometimes it’s about outcomes; results of procedures.
