I. Diagnostic Tests
|Disease Present||Disease Absent|
|Test result is Positive||A||B|
|Test result is Negative||C||D|
__A _ = "Sensitivity" aka "True Positive Rate"
A + C
__D _ = "Specificity" aka "True Negative Rate"
B + D
__A _ = "Positive Predictive Value"
A + B
__D _ = "Negative Predictive Value"
C + D
1 - Specificity = "False Positive Rate"
1 - Sensitivity = "False Negative Rate"
True Positive Rate_ = "Positive Likelihood Ratio"
False Positive Rate
False Negative Rate = "Negative Likelihood Ratio"
True Negative Rate
Probability___ = "Odds," often expressed as X:Y
1 - Probability
Odds of an event in one studied group_____ = "Odds Ratio"
Odds of same event in another studied group
"Reliability" = The ability of a test repeatedly to generate the same results given the same conditions
"Validity" = The degree to which a test measures what it is purported to measure
"Bias" = a systematic error that leads to results that do not represent the true findings
"Confounders" = Subject characteristics that are nonrandomly distributed between study groups that affect the results being studied and decrease its validity
II. Effects of Interventions
Events in Control Group - Events in Intervention Group = "Absolute Risk Reduction"
_________1_________ = "Number Needed to Treat"
Absolute Risk Reduction
Risk of disease in one group___ = "Relative Risk"
Risk of disease in another group
III. Other terms
"Incidence" = Number of new cases of a disease within a given time period in a given population
"Prevalence" = Number of cases of a disease in a population at a given time
"Kappa value" = A chance-corrected measure of inter-observer agreement. Perfect agreement = kappa of 1.0; absolute disagreement = kappa of 0. See Landis JR, Koch GG. The measurement of observer agreement for categorical data. Biometrics 1977;33:(1):159-74.