Biostatistics Flashcards
risk ratio
ratio of risk in the exposed group (treatment) divided by risk in the control group
Risk ratio =1 (or 100%)
no difference in risk of the outcome between the groups
Risk ratio >1 ( or >100%)
greater risk of the outcome in the treatment group
Risk ratio <1 ( or <100%)
lower risk of the outcome in the treatment group
Absolute risk reduction
includes the reduction in risk and the incidence rate of the outcome
(% risk in control group) - (% risk in treatment group)
Number needed to treat
number of patients who need to be treated for a certain period of time in order for one patient to benefit
1/ (risk in control) - (risk in treatment) or 1/ARR
Odds Ratio
the probability that an event will occur versus the probability tat it will not occur
Hazard Ratio
rate at which an unfavorable event occurs within a short period of time
OR or HR = 1
the event rate is the same in the treatment and control arms. There is no advantage to the treatment
OR or HR >1
The event rate in treatment group is higher than the event rate in the control group; for example, a HR of 2 for an outcome of death indicates that there are twice as many deaths in the group
OR or HR < 1
the event rate in the treatment group is lower than the event rate in control group; for example, a HR of 0.5 for an outcome of death indicates that there half as many deaths in the treatment group
Sensitivity
describes how effective a test identifies patients with the condition
Specificity
describes how effectively a test identifies patients without the condition
Intention-to-treat
includes data for all patients originally allocated to each treatment group even if the patient did not complete the trial according to the study protocol
Per protocol
conducted for the subset of the trial population who completed the study according to the protocol
Case-control study
compares patients with a disease to those without the disease
Cohort study
compares outcomes of a group of patients exposed and not exposed to a treatment
Cross-sectional study
estimates the relationship between variables and outcomes at one particular time in a defined population
Case report and case series
Describes an adverse reaction or a unique condition that appears in a single patient or a few patients
Randomized controlled trial
compares an experimental treatment to a control to determine which is better.
Parallel RCT
subjects are randomized to the treatment or control arm for the entire study
Crossover RCT
patients are randomized to one or two sequential treatments
Factorial design
Randomizes to more than the usual two groups to test a number of experimental conditions
Meta-Analysis
Combines results from multiple studies in order to develop a conclusion that has greater statistical power than is possible from the individual smaller groups
Systemic review article
summary of the clinical literature that focuses on a specific topic or questions
