mediation & moderation a primer, refresher, and clarification of terms
DESCRIPTION
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.” MODERATEDTRANSCRIPT
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?