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Nursing: MSN/DNP

Nursing

Biostatistical Terms

Biostatistical Term Abbreviation Definition
Sensitivity Sn Percentage of patients with disease who have a positive test for the disease in question.
Specificity Sp Percentage of patients without disease who have a negative test for the disease in question.
Predictive value (positive and negative) PV+
PV-
Percentage of patients with a positive or negative test for a disease who do or do not have the disease in question.
Pretest
probability
  Probability of disease before a test is performed.
Post-test
probability
  Probability of disease after a test is performed.
Likelihood ratio LR LR >1 indicates an increased likelihood of disease.
LR <1 indicates a decreased likelihood of disease.
The most helpful tests generally have a ratio of less than 0.2 or greater than 5.
Relative risk reduction RRR The percentage difference in risk or outcomes between treatment and control groups. Example: if mortality is 30% in controls and 20% with treatment, RRR is (30-20)/30 = 33 percent.
Absolute risk reduction ARR The arithmetic difference in risk or outcomes between treatment and control groups. Example: if mortality is 30% in controls and 20% with treatment, ARR is 30-20=10%.
Number needed to treat NNT The number of patients who need to receive an intervention instead of the alternative in order for one additional patient to benefit. The NNT is calculated as: 1/ARR. Example: if the ARR is 4%, the NNT = 1/4% = 1/0.04 = 25.
95% confidence interval 95% CI An estimate of certainty. It is 95% certain that the true value lies within the given range. A narrow CI is good. A CI that spans 1.0 calls into question the validity of the result.