Biostats 3 Flashcards
How do you calculate Sensitivity?
TP/(TP+FN)
How do you calculate Specificity?
TN/(TN+FP)
How do calculate +Predictive Value?
TP/(TP+FP)
How do calculate -Predictive Value?
TN/(TN+FN)
How do calculate +Likelihood Ratio?
Sensitivity/(1-Specificity)
How do calculate -Likelihood Ratio?
(1-Sensitivity)/Specificity
How do calculate Prevalence?
TP+ FN/(TP+ FP+FN+TN)
A False Positive is aka?
Type I error
A False Negative is aka?
Type II error
What is Sensitivity?
The ability of a test to single out those with disease as positive
● Percentage of persons with the disease of interest who have positive results
● If high sensitivity- a negative result rules out disease
What is Specificity?
The ability of the test to classify people who do not have illness as negative
● Percentage of persons without the disease of interest who have a negative test result
● If high specificity- a positive test result rules in disease
What does Positive Predictive Value do?
gives the frequency with which a positive test actually signifies disease
● Percentage of persons with positive test results who actually have disease of interest
Negative Predictive Value do?
gives the frequency with which a negative test identifies people without disease
● Percentage of persons with negative test who do not have the disease of interest
What is +LR?
probability of +test for a person with disease divided by probability of a +test for a person without disease (>10, high dx value), sens/ (1-spec)
How much more likely are we to find that a test is positive among patients with disease compared to those without disease?
What is -LR?
probability of –test for a person with disease divided by probability of a –test for a person without disease
