Public Health Sciences Flashcards
Cross-sectional study
Frequency of disease and frequency of risk- related factors are assessed in the present
Case-control study
Compares a group of people with disease to a group without disease.
Looks to see if odds of prior exposure or risk factor differs by disease state.
Odds ratio (OR).
Cohort study
Compares a group with a given exposure or risk factor to a group without such exposure.
Looks to see if exposure or risk factor is associated with later development of disease.
Relative risk (RR)
Clinical trial
SWIM
Evaluation of diagnostic tests
2x2 table
Disease on top
Test on the side
Sensitivity
(true- positive rate)
desirable for ruling out disease and indicates a low false-negative rate
High sensitivity test used for screening in diseases with low prevalence
= TP / (TP + FN)
= 1 – false-negative rate
Specificity
Desirable for ruling in disease and indicates a low false- positive rate
High speci city test used for con rmation after a positive screening test
= TN / (TN + FP)
= 1 – false-positive rate
Positive predictive value
Proportion of positive test results that are true positive
PPV = TP / (TP + FP)
Negative predictive value
Proportion of negative test results that are true negative.
NPV = TN / (TN + FN)
Quantifying risk
2x2 table
Disease on top
Risk factor/intervention on side
Odds ratio
ad/bc
Relative risk
[a/(a+b)]/[c/(c+d)]
Incidence vs. prevalence
Incidence= #new cases/# people at risk Prevalence= #existing cases/total # of people
Type I error (α)
Also known as false-positive error
Type II error (β)
Also known as false-negative error
