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DNP Doctor of Nursing Practice

Statistical Terms

Pre-Test Probability

Pretest Probability is defined as the probability of the target disorder before a diagnostic test result is known.

Likelihood Ratios

The Likelihood Ratio (LR) is the likelihood that a given test result would be expected in a patient with the target disorder compared to the likelihood that that same result would be expected in a patient without the target disorder.

Numbers Needed to Treat

The Number Needed to Treat (NNT) is the number of patients you need to treat to prevent one additional bad outcome (death, stroke, etc.).

SpPins and SnNouts


When a sign, test or symptom has an extremely high specificity (say, over 95%), a positive result tends to rule in the diagnosis.


When a sign, test or symptom has a high sensitivity, a negative result rules out the diagnosis.


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