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prob that patient with a disease will have positie test result, won't miss people with a disease, rules out those without dz (few false neg)
prob that patient without disease will have a negative test result, rules in those with disease (low false positive)
False neg and false positive ratio
False neg ratio=1-sens
False pos ratio=1-spec
prob that patient with a positive test actually has disease, more specific=high ppv, higher disease prevalence, higher ppv
- prob that patient with neg test result doesnt have disease, more sensitive, higher nov.
- lower disease prev, higher npv
Positive likelihood radio
- Fraction of patients with a disease who have a positive test divided by those without a disease who have a positive test
- Shows the probability of a disease if the test is +
negative likelihood ratio
- shows prob of disease are dec if test neg
- group of people assembled none who has the outcome of interest(the disease) but all who could experience that outcome. Followed over time and incidence of outcome is compared over exposure groups
- Can be prospective or retrospective
Case control study
- series of cases identified and a set of controls sampled from the underlying pop to estimate the frequency of exposure in the population at risk of outcome. Compares frequency of exposure to a possible risk factor in two groups.
- Ex: alcohol intake among individuals with breast cancer compared to that of people without breast cancer
- incidence in exposed people/incidence in unexposed
- estimate of relative risk that is used in case control studies
- odds that disease person is exposed/odds that non diseased person is exposed