BIOSTATISTICS Flashcards
What’s lead time bias?
Is the erroneous finding of prolongation of survival when just the illness was detected earlier .
What’s latent period factor in the effect of drugs or change in the risk?
Period needed to show differences
What is Observer bias ?
Is when the observer misclassifies data according its interpretation or its expectations
What’s selection bias ?
Inappropriate non-random selection
When use odds ratio?
CASE-CONTROL STUDIES !!!
RETROSPECTIVE!!!!
OR=ad/bc
“Patients with COPD had higher odds of a
history of smoking than those without COPD.”
When use Relative Risk?
COHORT STUDIES!!!!
PROSPECTIVE!!!!!
RR=[a/(a+b)] / [c/(c+d)]
“Smokers had a higher risk of developing COPD
than nonsmokers.”
What’s selection bias ?
Selection of unrepresentative sample ( all healthy ,all sick)
ATTRITION BIAS : a very different group of data is loss
What’s missclassification bias?
Use the wrong method to classify the groups
Big difference between case-control and cross-sectional study?
CASE -CONTROL : Make sick and non-sick subjects
CROSS-SECTIONAL: take random subjects
Big characteristic of randomized clinical trial?
COMPARES >2 TREATMENTS
What’s type II(beta) error?
Falsely conclude there is NO difference
FALSELY NOT REJECT
What’s type I (alpha) error?
Falsely conclude there is a difference
Falsely REJECT
The best answer to a college asking about a patient of your is …
No, I cannot say whether she is my patient .
How confounding bias can be controlled?
MATCHING
used in case control studies
Matching the subjects by age , race , gender etc…
What is statistical power?
1-beta
SAMPLE SIZE
Cause of mortality in TCAs overdoses?
Cardiac arrhythmia say inhibit fast Na channels
Refractory hypotension by alpha agonist
What is the center of study of ECOLOGICAL STUDY?
COMPARE POPULATIONS!!!!!!!
used to make HYPOTHESIS NOT CONCLUSIONS!!!!
What’s nested case-control?
Begins whit cohort studies
The patients with the outcome go to case - control studies
How the protest probability affects the NEGATIVE PREDICTIVE VALUE?
⬇️Pre-test probability ⬆️ NPV
⬆️Pre-test probability ⬇️ NPV
What is near miss?
Error recognized before any harm
What’s sentinels event?
Unexpected event involving death or serious physical or psychological injury that’s REQUIERS IMMEDIATE INVESTIGATION
Which calculation can be used to comparete different tests whit different normal values?
Coefficient variance
What’s a reliable test?
A test whit very similar results in the same patient is REPRODUCIBLE
What’s a valid test ?
Is the ability to measure what is suppose to measure
Very similar whit GOLD STANDARD
