D-score Chapter I
Preface
1
Introduction
1.1
First 1000 days
1.2
Relevance of child development
1.3
Stunting as proxy for child development
1.4
Measuring neurocognitive development
1.5
Why this chapter?
1.6
Intended audience
2
Short history
2.1
What is child development?
2.2
Theories of child development
2.2.1
Continuous or discontinuous?
2.2.2
One course or multiple parallel tracks?
2.2.3
Nature or nurture?
2.3
Example of motor development
2.3.1
Shirley’s motor data
2.3.2
Individual trajectories of motor development
2.4
Typical questions asked in child development
3
Quantifying child development
3.1
Age-based measurement of development
3.1.1
Motivation for age-based measurement
3.1.2
Age equivalent and developmental age
3.1.3
Limitations of age-based measurement
3.2
Probability-based measurement
3.2.1
Example of probability-based measurement
3.2.2
Limitations of probability-based measurement
3.3
Score-based measurement of development
3.3.1
Motivation for score-based measurement
3.3.2
Example of score-based measurement
3.3.3
Limitations of score-based measurement
3.4
Unit-based measurement of development
3.4.1
Motivation for unit-based measurement
3.4.2
Example of unit-based measurement
3.4.3
Limitations of unit-based measurement
3.5
A unified framework
3.6
Why unit-based measurement
4
The D-score
4.1
The Dutch Development Instrument (DDI)
4.1.1
Setting
4.1.2
Description of SMOCC study
4.1.3
Codebook of DDI 0-30 months
4.2
Probability of passing a milestone given age
4.3
Probability of passing a milestone given D-score
4.4
Relation between age and the D-score
4.5
Measurement model for the D-score
4.5.1
What are measurement models?
4.5.2
Adapt the model? Or adapt the data?
4.6
Item response functions
4.6.1
Logistic model
4.6.2
Types of item response functions
4.6.3
Person response functions
4.7
Engelhard criteria for invariant measurement
4.8
Why take the Rasch model?
5
Computation
5.1
Identify nature of the problem
5.2
Item parameter estimation
5.2.1
Pairwise estimation of item difficulties
5.2.2
Anchoring
5.3
Estimation of the D-score
5.3.1
Role of the starting prior
5.3.2
Starting prior: Numerical example
5.3.3
EAP algorithm
5.3.4
EAP algorithm: Numerical example
5.3.5
Technical observations on D-score estimation
5.4
Age-conditional references
5.4.1
Motivation
5.4.2
Estimation of the reference distribution
5.4.3
Conversion of
\(D\)
to DAZ, and vice versa
6
Evaluation
6.1
Item fit
6.1.1
Well-fitting item response curves
6.1.2
Item response curves showing severe underfit
6.1.3
Item response curves showing overfit
6.1.4
Item infit and outfit
6.1.5
Infit and outfit in the DDI
6.2
Person fit
6.2.1
Person infit and outfit
6.2.2
Person infit and outfit in the DDI
6.3
Differential item functioning (DIF)
6.3.1
Relevance of DIF for cross-cultural equivalence
6.3.2
How to detect DIF?
6.3.3
Examples of DIF
6.4
Item information
6.4.1
Item information at a given ability
6.4.2
Item information at a given age
6.5
Reliability
7
Validity
7.1
Internal validity
7.1.1
Content validity
7.1.2
Construct validity
7.2
External validity
7.2.1
Discriminatory validity
7.2.2
Convergent and divergent validity
7.2.3
Predictive validity
8
Precision
8.1
SMOCC design: Standard and additional milestones
8.2
D-score from short tests
8.2.1
Milestone sets
8.2.2
Milestone sets at month 2
8.2.3
Milestone sets at month 3
8.2.4
Floor and ceiling effects
8.3
Impact of short tests on predicting IQ
8.3.1
Measurement and prediction
8.3.2
UKKI
8.3.3
Exploratory analysis
9
Three studies
9.1
SMOCC study
9.2
POPS study
9.2.1
POPS design
9.2.2
Age-adjustment
9.2.3
Effect of age-adjustment on the D-score
9.2.4
Effect of no age adjustment (
\(f = 0.00\)
) on the DAZ
9.2.5
Effect of full age adjustment (
\(f = 1.00\)
) on the DAZ
9.2.6
Partial age adjustment
9.2.7
Conclusions
9.3
TOGO study
9.3.1
Togo Kpalimé study, design
9.3.2
D-score labelled by neurological problem
9.3.3
D-score labelled by Apgar score
9.3.4
D-score labelled by severe underweight
9.3.5
D-score labelled by severe stunting
9.3.6
Gross motor development
9.3.7
Fine motor development
9.3.8
Communication and language
9.4
Conclusions
10
Next steps
10.1
Usefulness of D-score for monitoring child health
10.2
D-chart, a growth chart for child development
10.3
Opportunities for early intervention
10.4
D-score for international settings
10.5
D-score from existing instruments
10.6
Creating new instruments for D-score
Appendices
A - Notation
B - Project information
Data availability
Grant information
Competing interests
C - Technical information
References
Child Development with the D-score
Grant information
This work was supported by the Bill & Melinda Gates Foundation, Investment ID 52561.