Statistics Flashcards
What are the two main types of studies?
Observational vs experimental (trials)
What are the types of observational studies?
Cohort, case control
What are cohort studies used for?
- Prospectively following a group of people and observing if an exposure increases a certain outcome
What are case control studies used for?
- Rare diseases that are uncommon
- Start with the outcome (rare disease) and look retrospectively to identify whether they were exposed to a risk or not
What is random error?
uncontrollable error due to random chance, can be reduced by increased sample size
What is bias?
Systematic deviation from the truth
Increased sample size doesn’t reduce this
What are types of bias?
Selection
Measurement
Publication
Can happen at any stage of research
What criteria is used to try and define causation?
Bradford Hill’s
What is a type I error?
False positive
What is a type II error?
False negative
What are descriptive statistics?
describe data and results
eg: central tendency (mean - average, mode - most common, median - middle)
dispersion (Range, IQR, st deviation)
accuracy: Confidence interval
Risk ratio (where you know the number exposed i.e RCT)
Odds ratio (where you don’t know the number exposed eg Case control)
What are inferential statistics?
- Applying tests to data to try and accept or reject the null hypothesis
What is sensitivity?
Ability to pick up positive patients.
SnOUT: if test is highly sensitive and you’re negative, its likely to be negative
Risk: False positives (overcalls positives to find them all!)
What is specificity?
Ability to pick up negative patients
SpIN: If test is highly specific and you’re positive, its likely to be positive
Risk: False negatives (overcalls negatives to find them all)
