# Effect modification. Flashcards

1
Q

When does Effect Modification occur?

A

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

2
Q

Do you modify for effect modification?

A

No. It is not an error.

3
Q

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

A

Stratum specific OR’s.

4
Q

How do you evaluate stratum specific OR’s?

A
1. Calculate P values on homogeneity tests.

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

5
Q

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

A

Breslow-day test.

6
Q

What is the conceptual definition of an effect modifier?

A

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

7
Q

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

A

Statistically different.

8
Q

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

A

The confidence intervals.

9
Q

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

A

Report confounders separately.

10
Q

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

A

H0= OR1=OR2

11
Q

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

A

H1= OR1 is not equal to OR2.

12
Q

What distribution is used in the Mantel-Haenzsel test?

A

Chi squared to 1 dof.

13
Q

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

A

Stratum specific OR’s are homogenous.

14
Q

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

A

Linear, Poisson.

15
Q

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

A

Logistic, poisson, survival (COX) analysis.

16
Q

What does the side of an interaction effect influence?

A

The size of the sample needed to detect its effect.

17
Q

What is another name for effect modification?

A

Biological modification.

18
Q

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

A
1. Chance.
2. Systematic error.
3. Varying exposure doses between strata.
19
Q

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

A

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

20
Q

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

A

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

21
Q

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

Belongs to a specific study.

A

Confounder.

22
Q

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

Exists in nature.

A

Effect Modifier.

23
Q

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

Different effects in different strata.

A

Effect modifier.

24
Q

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

Increases biological knowledge of mechanism.

A

Effect modifier.

25
Q

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

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

A

Confounder.

26
Q

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

Creates confusion in the data.

A

Confounder.

27
Q

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

Allows targeting of public health outcome.

A

Effect modifier.