Critical Appraisal Flashcards
Define Validity
Is the finding true
Define Generalisability
Is the finding applicable elsewhere?
3 reasons for not being valid
Chance (random error) —- (finding imprecise) Bias (systematic error) —- (finding inaccurate) Confounding (error of interpretation) —- (beware, unknown confounders cannot be statistically accounted for)
Define
Efficacy
Vs
Effectiveness
Efficacy: Shows if something works under ideal conditions
Vs
Effectiveness: shows if something works under normal conditions
Types of research Qs:
Pragmatic research
Vs
Explanatory research
Pragmatic research - demonstrates effectiveness Vs Explanatory research - demonstrated efficacy
Aspects of
Pragmatic research
Unselected population
Pt centred outcomes
Does not interfere with clinical practice
Aspects of
Explanatory research
Can it work under ideal conditions
Specific staff/setting/population
Often clinical outcome
Null hypothesis
Define
No difference between active treatment and placebo
P value
Define
Chance null hypothesis is true
Type 1 error =
False positive (p value)
Type 2 error =
False negative
Statistical significance =
alpha + beta
Define a+b
Alpha
- maximum possibility of a false positive (p value)
Beta
- max possibility of false negative
(Determined by sample size)
Power of study =
1- beta
Beta = max possibility of a false negative
Usually set to 80-90%
Study power is set by
- Level of alpha
- Sample size
- The minimum clinical difference you wish to detect
Issue with multiple hypothesis testing:
Increases false positive
- only use if there is a clear rationale to the test
Benefit of randomisation
Removes confounders
Concealment prevents
Allocation bias
Blinding prevents
Measurement bias
Outcome bias
More likely if
Soft outcomes