Study design, statistics Flashcards
What is a case-control study?
A retrospective study examining the rates of exposure in diseased vs healthy individuals
What is a cohort study?
A prospective study examining the rates of disease in exposed vs nonexposed individuals
Which is better, case-control or cohort study?
Cohort study allows for a calculation of relative risk
Case-control can only estimate, not establish causality and gives an odds ratio
What is one of the main types of bias in case-control studies?
Recall bias
What is one of the main types of bias with cohort studies?
Attrition bias
Describe the types of studies
Descriptive vs analytical
Analytical can be experimental vs observational
Descriptive: case report/series
Observational: case-control, cohort, cross-sectional
Experimental: RCTs
What is a cross-sectional study?
Examining a population at a given time point to find the frequency of disease/risk factors eg. frequency of migraine in the obstetric population
What are the phases of clinical trials?
Phase I: safety (small numbers). Not randomised. Monitoring doses + side effects.
Phase II: efficacy. Often randomised.
Phase III: compare to best current treatment. Randomised.
Phase IV: post-licensing. Large scale efficacy, long term side effects.
How is SD calculated?
Square root of the variance (take difference of each value from mean, square them, sum all together, divide by n-1)
How is SEM calculated?
SD / square root of n
How are 95% CI calculated?
+/- 1.96 * SEM
