biostatistics & pharmacoeconomics Flashcards
RR equation
risk in tx group / risk in control group
RR interpretation
RR >1 greater risk of outcome in tx
RR <1 lower risk
RR = 1 same risk
patients are AS LIKELY to have disease progression as placebo group
RRR equation and interpretation
1 - RR
LESS LIKELY to have progression
ARR equation and interpretation
(% risk in control) - (% risk in tx)
x out of every 100 patients benefit from treatment OR for every 100 patients, x fewer will have disease progression
NNT and NNH equation
1 / ARR
ROUND UP for NNT
ROUND DOWN for NNH
odds ratio equation
AD / BC
hazard ratio equation
hazard rate in tx / hazard rate in control
what is ratio data
continuous
0 = NONE
what is interval data
continuous
0 does not = NONE
what is nominal data
categorical/discrete
age, gender, mortality
what is ordinal data
categorical/discrete
pain scale, NYHA class
what type of data will have a gaussian distribution
large sample sets of continuous data
examples of independent variables
drugs, doses, placebos, patients
anything changed by the researcher
examples of dependent variables
HF progression, BP, mortality
the effect from the independent variable
CI equation
CI = 1 - alpha
how do you interpret confidence intervals
statistically significant if the CI range does not include or p value is < alpha
how do you interpret confidence intervals for relative risk, odds ratio, hazard ratio
statistically significant if the CI range does not include 1
type I error
false positive
null hypothesis was rejected in error
type II error
false negative
null hypothesis was accepted when it should have been rejected
what is the significance of study power
1 - Beta
the probability that a test will reject the null correctly (the power to avoid a type II error)
types of tests for continuous data
one sample t test for 1 group
paired t test for before & after of 1 group
student t test for 2 groups
ANOVA for >3 groups
types of tests for categorical data
chi squared test
sensitivity equation and interpretation
A / A+C x 100
test is positive in x% of patients that have disease
specificity equation and interpretation
D / B+D x 100
test is negative in x% of patients without disease
case control study
compares patients with a disease to those without
retrospective
cohort study
compares outcomes of a group exposed and not exposed to treatment
prospective or retrospective
incremental cost effectiveness ratio equation
(C2 - C1) / (E2 - E1)
cost minimization analysis
costs of each intervention are compared
(two ACEi are considered equivalent, but the costs are different)
cost benefit analysis
compares benefits and costs of an intervention
cost effectiveness analysis
compares effects to costs
cost utility analysis
QALYs
