Effect modification.

Question 1

When does Effect Modification occur?

Answer 1

When the strength of association varies over different categories of a third variable in an association study.

Question 2

Do you modify for effect modification?

Answer 2

No. It is not an error.

Question 3

What OR’s do you look at when looking at effect modification?

Answer 3

Stratum specific OR’s.

Question 4

How do you evaluate stratum specific OR’s?

Answer 4

1. Calculate P values on homogeneity tests.

2. Evaluate overlap of CI’s on stratum specific OR’s.

Question 5

What homogeneity test do you use to calculate the p values for effect modification?

Answer 5

Breslow-day test.

Question 6

What is the conceptual definition of an effect modifier?

Answer 6

The effect of the exposure and potential modifier differ from the expected joint effect.

Question 7

For something to be an effect modifier what must the OR be after stratifying?

Answer 7

Statistically different.

Question 8

When will an effect modifier be described as being in the ‘grey zone’ what is overlapping?

Answer 8

The confidence intervals.

Question 9

Apart from using the Mantel-Haenzsel OR what other way can you adjust for confounding?

Answer 9

Report confounders separately.

Question 10

What is the equation for the null hypothesis for the Mantel-Haenzsel test?

Answer 10

H0= OR1=OR2

Question 11

What is the alternative hypothesis for the Mantel-Haenzsel test?

Answer 11

H1= OR1 is not equal to OR2.

Question 12

What distribution is used in the Mantel-Haenzsel test?

Answer 12

Chi squared to 1 dof.

Question 13

In words what is the null hypothesis for the Mantel-Haenzsel test?

Answer 13

Stratum specific OR’s are homogenous.

Question 14

What sort of regression models are used to look at additive effects?

Answer 14

Linear, Poisson.

Question 15

What sort of regression models are used to look at multiplicative effects?

Answer 15

Logistic, poisson, survival (COX) analysis.

Question 16

What does the side of an interaction effect influence?

Answer 16

The size of the sample needed to detect its effect.

Question 17

What is another name for effect modification?

Answer 17

Biological modification.

Question 18

Interactions can be seen to occur when they do not actually exist. Why? (3 things).

Answer 18

1. Chance.
2. Systematic error.
3. Varying exposure doses between strata.

Question 19

When does qualitative effect modification occur instead of quantitative? What does this mean?

Answer 19

When measures of effect in different strata have different directions. This means that effect modification occurs on both the multiplicative and additive scale.

Question 20

Explain the phenomenon of reciprocity in terms of effect modifier Z, exposure E and outcome D.

Answer 20

If Z modifies the effect of E on D than Z also modifies the effect of E on D.

Question 21

Does the following statement describe an effect modifier or a confounder?

Belongs to a specific study.

Answer 21

Confounder.

Question 22

Does the following statement describe an effect modifier or a confounder?

Exists in nature.

Answer 22

Effect Modifier.

Question 23

Does the following statement describe an effect modifier or a confounder?

Different effects in different strata.

Answer 23

Effect modifier.

Question 24

Does the following statement describe an effect modifier or a confounder?

Increases biological knowledge of mechanism.

Answer 24

Effect modifier.

Question 25

Does the following statement describe an effect modifier or a confounder?

Prevented in the design stage, controlled for in analysis stage.

Answer 25

Confounder.

Question 26

Does the following statement describe an effect modifier or a confounder?

Creates confusion in the data.

Answer 26

Confounder.

Question 27

Does the following statement describe an effect modifier or a confounder?

Allows targeting of public health outcome.

Answer 27

Effect modifier.