Mediation & ModerationA PRIMER, REFRESHER, AND CLARIFICATION OF TERMS

Blimpo & Evans, 2011

“We found that the effect of the WSD program on learning outcomes is strongly mediated by the baseline local capacity measured by

adult literacy.”

Blimpo & Evans, 2011

“We found that the effect of the WSD program on learning outcomes is strongly mediated by the baseline local capacity measured by

adult literacy.”MODERATED

Blimpo & Evans, 2011

“We found that the effect of the WSD program on learning outcomes is strongly mediated by the baseline local capacity measured by adult literacy.”

WSD Program Receipt

Baseline Local

Capacity

Measured Student Learning

* *

Blimpo & Evans, 2011

“We found that the effect of the WSD program on learning outcomes is strongly mediated by the baseline local capacity measured by adult literacy.”

WSD Program Receipt

Baseline Local

Capacity

Measured Student Learning

* *wave 1, pre-treatment

implemented between waves 1 & 2

Blimpo & Evans, 2011

“We found that the effect of the WSD program on learning outcomes is strongly mediated by the baseline local capacity measured by adult literacy.”

moderated

WSD Program Receipt

Baseline Local

Capacity

Measured Student Learning

*

Agenda

Moderation

Mediation

Mediated Moderation

Moderated Mediation

MODERATION

CHANGES STRENGTH OF RELATION BETWEEN TWO VARIABLES

FOR WHOM UNDER WHAT CONDITIONS

“partitions a focal independent variable into subgroups that establish its domains of maximal effectiveness in regard to a given dependent variable” (Baron & Kenny, 1986)

Moderation

Independent Variable (X)

Outcome Variable

(Yi j)

Potential Moderator

(Mod )

𝜸𝟎𝟑

𝜸𝟎𝟏

𝜸𝟎𝟐

+

Moderation

Do girls experience a greater increase in confidence than boys after an intensive math intervention?

Does the program work better or worse in urban areas as compared to rural ones?

Is program impact higher where implementation fidelity was greater? Does the informational intervention about health prevention operate more

effectively in communities with localized health services?

MEDIATION

INTERVENING OR PROCESS VARIABLE

HOWWHY

“represents the generative mechanism through which the focal independent variable is able to influence the dependent variable of interest” (Baron & Kenny, 1986)

Mediation

Independent Variable (X)

Outcome Variable

(Yi j)

Indirect effect = ab

Potential Mediator

(Med ) a b

c

4 conditions for mediation*

1) The treatment is correlated with the outcome: c path is significant2) The treatment is correlated with the potential mediator: a path is significant3) The mediator is correlated with the outcome when controlling for treatment:

b path is significant4) The effect of the treatment on the outcome is reduced when controlling for

the potential mediator: c’ is zero (full mediation) or non-significant (partial mediation)

Mediation

Do students experience a greater increase in confidence after an intensive math intervention because or in accordance with how much their ability improves?

Does the program increase health outcomes through reducing wait time in the local health clinic?

Does the school intervention increase test scores through changing teachers’ instructional styles?

Do conditional cash transfers impact child health outcomes through increasing vaccination rates?

Quiz!

A conditional cash transfer to families leads to payment of school fees which increases children’s enrollment school.

MEDIATOR MODERATOR

Quiz!

A school-based socioemotional learning program in a conflict-affected countries improves children’s mental

health, but not for children who witnessed prolonged and severe violence.

MEDIATOR MODERATOR

MEDIATED MODERATION

What are the mediating processes through which the

intervention produces differential effects?

• Can only happen when the treatment effect is moderated

• Different ways for a moderated treatment effect to occur

Moderation

Do girls experience a greater increase in confidence than boys after an intensive math intervention because their ability increases more than boys due to the intervention?

Does the informational intervention about health prevention operate more effectively in communities with localized health services because visits to the health center increase by the most in those communities?

MODERATED MEDIATION

The mediating process that is responsible for producing the

effect of the intervention on the outcome differs as a function of

individual differences or context.• Implies identifying a mediating

effect; but does not imply overall moderation of the treatment effect

• Different ways for moderated mediation to occur

Moderated Mediation

On average, all students experience a greater increase in confidence after an intensive math intervention. Does this operate through increasing actual, measured aptitude in boys and through increasing perceptions of aptitude in girls?

Do conditional cash transfers impact child health (i.e. mortality) outcomes through increasing vaccination rates in communities with low baseline vaccination rates and through increasing nutritional intake in communities with higher baseline vaccination rates?

Questions?