ADI Final

hazard function

analyzes the likelihood that an item will survive to a certain point in time based on its survival to an earlier time

number needed to treat

average number of patients who need to be treated to prevent one additional bad outcome inverse of the absolute risk reduction

confounding can be dealt with

by randomization, matching, stratification analysis, or multiple regression analysis

Log-Rank Test

compare survival curves

OR = 1

disease/ outcome and exposure are independent

RR = 1

disease/ outcome and exposure are independent

number needed to harm

how many persons on average need to be exposure to a risk factor over a specific period to cause harm in an average of one person who would not otherwise have been harmed inverse of the absolute risk increase

disadvantage of stratification

inability to control simultaneously for multiple confounding variables

when less effective treatment is applied more frequently to less severe cases,

it can appear to be a more effective treatment

censoring

key feature of survival data occurs when we have some information about individual's survival time but we don't know the exact survival time

Odd Ratio

must be a positive number is symmetric (reversing the roles of disease and exposure makes no difference) (a)(d) / (b)(c)

Relative Risk (Risk Ratio)

must be positive not symmetric

confounding

occurs when the relationship between exposure/ treatment and disease/ outcome is distorted by the influence of a third variable or group of variable (confounders)

Mantel-Haenszel Method

pooling method that combines stratum-specific RRs or ORs

hazard rate

rate of death for an item of a given age

as you increase the number of strata,

sample size becomes a major problem because many of the strata contain few or no people

Cochran-Mantel-Haenszel Test

statistical test for assessing association between exposure/ treatment and disease/outcome, controlling for confounding

survival function

the chance that an individual is still alive after time t

OR is approximately equal to RR when..

the disease is rare

Non-Inferior Margin

the predetermined margin of difference between the new and standard treatments

OR > 1

there is a greater odds of disease/ outcome when exposed than unexposed

RR > 1

there is a greater risk of disease/ outcome when exposed then unexposed

OR < 1

there is less odds of disease/ outcome when exposed than unexposed

RR < 1

there is less risk of disease/ outcome when exposed than unexposed

Why are RR and OR used?

to quantify the relationship between exposure and disease