Statistics Flashcards
What is power in biostatistics?
The probability that your study will detect the effect of a treatment if present. The higher the better in terms of detecting the effect
What are type 1 and type 2 errors in biostatistics?
Type 2 error - underpowered
Type 1 error - false positive rate because thee multiple comparison were not adequately adjusted for
what is alpha in calculating power estimate?
alpha - set by you but typically 0.05 (false positve rate - meaning, 5% of the time you may find significant related to sampling error)
What is the mathematical relationship between sample size and effect size when doing a power analysis (estimate)?
N - sample size
Delta - effect size: the expected difference (mean, RR, proportions)
alpha - set by yyou but typically 0.05 (false positve rate - meaning, 5% of the time you may find significant related to sampling error)
beta - failing to say there is a difference (accepting null), so 1-beta is th probability you will find a difference
what is beta in calculating power estimates?
beta - failing to say there is a difference (accepting null), so 1-beta is th probability you will find a difference
PICO question for clinical trials:
P - population
I - intervention
C - comparison
O - outcome
What is a cohort study?
Group of people with similar risks but have different exposures
What is a case study?
What are advantages to a cohort study?
Gather data regarding sequence of events; can assess causality
Examine multiple outcomes for a given exposure
Good for investigating rare exposures
Can calculate rates of disease in exposed and unexposed individuals over time (e.g. incidence, relative risk)
What are disadvantages to cohort study?
Large numbers of subjects are required to study rare exposures
Susceptible to selection bias
Prospective Cohort Study
May be expensive to conduct
May require long durations for follow-up
Maintaining follow-up may be difficult
Susceptible to loss to follow-up or withdrawals
Retrospective Cohort Study
Susceptible to recall bias or information bias
Less control over variables
What are advantages of case studies?
Good for examining rare outcomes or outcomes with long latency
Relatively quick to conduct
Relatively inexpensive
Requires comparatively few subjects
Existing records can be used
Multiple exposures or risk factors can be examined
What are disadvantages of case-control studies?
Susceptible to recall bias or information bias
Difficult to validate information
Control of extraneous variables may be incomplete
Selection of an appropriate comparison group may be difficult
Rates of disease in exposed and unexposed individuals cannot be determined
Types of study design:
