Stats and CAT stuff Flashcards
What is a 95% confidence interval?
The range of values that are 95% certain to contain the true value
What is standard deviation?
A value that shows how much variation there is from the mean
What is a P-value, & what is the cut off?
- A value that shows how likely it is that results are due to chance
- P>0.05 is not statistically significant
What is power?
The probability of correctly reject the null hypothesis when it is false
What is the purpose of blinding?
- To reduce conscious or subconscious bias
What is concealment of allocation, and what bias does it reduce?
- When someone running a trial doesn’t know what group a participant will be put in
- Reduce selection bias
What is intention to treat analysis, and give an example of when it may be used?
- Analysis based the initial intended intervention rather than what was ultimately given
- Can be used when someone drops out of a study
What is treatment fidelity?
How well an intervention is reproduced from a protocol or animal model
What is the purpose of randomisation?
- To equally distribute possible confounding factors between different study groups
- Reduces selection bias
What is internal validity?
- Accuracy
- How well a study is conducted, taking into account confounders and removing bias
What is external validity?
- Generalisability
- How well can the results of a study be applied to different patients, situations and environment in the real world
What is a type 1 error?
- Rejecting the null hypothesis when it is true
- False positive
What is a type 2 error?
- Accepting the null hypothesis when it is false
- False negative
What is absolute risk?
The risk of disease/death in the population being studied
What is relative risk?
The risk of disease/death in the exposed, compared to that in the non-exposed
What is the risk ratio?
Probability of disease/death in the at-risk group/that of the not-at-risk group
What is the odds ratio?
Ratio of odds of disease/death in exposed, compared to that of the non-exposed
What is absolute risk reduction?
Rate of disease/death in the unexposed minus the rate in the exposed
What is the formula for absolute risk reduction?
CER-EER
What is attributable risk?
- Rate of disease/death in exposed minus the rate in unexposed
- (opposite of absolute ARR)
- (think of it as the actual risk that can be ATTRIBUTED to a risk factor by removing the natural rate of developing a disease in the unexposed)
What is the formula for attributable risk?
EER-CER
What is a hazard ratio, and when might it be used?
- Similar to relative risk, but when a risk isn’t constant to time
- E.g. when looking at survival time
What is numbers needed to treat, and how should you deal with a decimal NNT figure?
- The number of people required to receive an intervention to produce 1 positive outcome
- Always round up
What is numbers needed to harm, and how should you deal with a decimal NNH figure?
- The number of people required to receive an intervention to produce 1 adverse outcome
- Always round down