Statistics

TEST TAKING TIPS

What is sensitivity?

• Proportion of truly diseased persons in a screened population who are identified as being diseased by the test. It is a measure of the probability of correctly diagnosing a condition.

Sensitivity equation:

• True positive/(true positive + false negative)

What is specificity?

• The proportion of truly nondiseased persons who are so identified by the screening test

Specificity equation:

• True negative/(false positive + true negative)

False-positive rate:

• 1 – specificity

False-negative rate

• 1 – sensitivity

What is positive predictive value?

• The probability that a person with a positive test result has the disease

What is the positive predictive equation?

• True positive/(true positive + false positive)

What is the negative predicted value?

• The probability that a patient with a negative test result really is free of the disease

What is the negative predicted value equation?

• True negative/(false negative + true negative)

Definition of prevalence:

• The total number of cases of a given disease in a specified population at a designated time

Definition of incidence:

• The number of new cases of a given disease during a given period in a specified population

What is the absolute risk reduction?

• The absolute arithmetic difference in outcome rates between control and experimental patients in a trial

What is relative risk reduction?

• The proportional reduction in outcome rates between control and experimental patients in a trial

A range of values that has a specified probability of containing the rate or trend:

• Confidence intervals

A method of studying a drug or procedure in which both the subjects and investigators are kept unaware of who is actually getting which specific treatment:

• Double-blind method

The number of patients who need to be treated to prevent one adverse outcome:

• Number Needed To Treat

The probability that an event will occur:

• Risk

The number of units in a population to be studied:

• Sample size