bias and confounding

Question 1

internal validity

Answer 1

study representative of reality of study participants

Question 2

external validity

Answer 2

are the results representative of reality of other populations and at other times

Question 3

reliability

Answer 3

chances of getting similar results after repeating the test

Question 4

how to prevent random errors

Answer 4

well planned study
adequate sample size
quality check
measurement tools

Question 5

random error

Answer 5

occurs randomly cannot be predicted

Question 6

selection bias

Answer 6

systemic error in the sampling process

Question 7

information bias

Answer 7

error in the process of collecting and analyzing info
differential if linked to exposure
non differential

Question 8

how to prevent selection bias

Answer 8

Representative sample
Well written, clear protocols
Criteria for inclusion and exclusion well documented and understood
Minimise attrition

Question 9

How to prevent information

Bias

Answer 9

exposure and outcome criteria must be clear
adequate staff training
validate data, test tools and conduct a pilot study
subjects and observers should be blinded

Question 10

how to control confounding during study

Answer 10

randomization
matching - individual matching, cases and controls have the same confounders
restriction

Question 11

how to control confounding during study

Answer 11

stratification
standardization
multivariable regression