Lecture 8 - Confounding and effect

Question 1

define confounding

Answer 1

the mixing of the effect of exposure with effect of another factor

Question 2

define confounder

Answer 2

disease risk factor thats independent of exposure, associated with exposure but not a consequence of exposure and not in the causal pathway

Question 3

define stratified analysis

Answer 3

test association (OR) btw exposure and outcome separately within each level of confounder

Question 4

what are the design aspects of managing confounders

Answer 4

randomization, restriction, matching

Question 5

define restriction

Answer 5

limit entrance to subjects who fall in one category of confounder

Question 6

what are the problems of randomization

Answer 6

cant randomize in an observational study

Question 7

what are the problems of restriction

Answer 7

reduce @ of participants, residual confounding, cant study effect of other counfounding category

Question 8

what are the analysis aspects of managing confounders

Answer 8

multivariable regression analysis or stratification

Question 9

what is multivariable regression analysis

Answer 9

method for studying relationship btw 1 dependent variable (criterion) and 2 independent variables (predictor variable)

Question 10

what is the design of a multivariable regression analysis

Answer 10

10x as many cases as independent variables

Question 11

what is the purpose of multivariable regression analysis

Answer 11

theory building, prediction, explanation

Question 12

What are the 4 things a confounder can do?

Answer 12

1. wipe out association 2. create an invalid association 3. reverse direction of association 4. change degree of association

Question 13

define effect modification

Answer 13

3rd variable that changes relationship btw exposure and outcome

Question 14

define effect modifier

Answer 14

exposure-disease relationship differs at diff levels of effect modifier

Question 15

confounder effect on exposure-disease relationship ______ at diff levels of confounder

Answer 15

stays the same

Question 16

what is the equation for stratified analysis

Answer 16

manzel haenzsel method

Question 17

What does mantel haenszel method provide

Answer 17

a pooled odds ratio across the strata of fourfold table

Question 18

what does mantel haenszel estimator measure

Answer 18

measure of the average effect of exposure across all strata

Question 19

mantel haenszel accounts for what

Answer 19

confounding and effect modifier

Question 20

where does the mantel haenszel measure lie

Answer 20

btw OR/RR strat 1 and OR/RR strat 2

Question 21

if crude OR/RR falls outside range of stratum specific OR/RR, what can u interpret

Answer 21

crude does not equal average of data and shouldnt be used

Question 22

a third variable can be ….

Answer 22

confounder, EM, both or neither

Question 23

it is a confounder if

Answer 23

crude does not equal MH, and strat 1 equals strat 2

Question 24

it is an effect modifier if

Answer 24

crude equals MH, and strat 1 does not equal strat 2

Question 25

it is both an effect modifier and confounder if

Answer 25

crude does not equal MH, and strat 1 does not equal strat 2

Question 26

it is neither an effect modifier and confounder if

Answer 26

everything is equal (crude, MH, strat 1, and strat 2)