IELS 2018 Design

Quantitative Study

Overall approach to data collection

  • Proctored assessment of children’s skills
  • Self-administered questionnaires for parents and teachers
Target population

All children in centers/schools at the age of five at the time of the assessment

Sample design
Stratified two-stage probability sampling design

First stage: Sampling centers/schools

  • Probability proportional to size (PPS), i.e., the expected number of eligible children
  • Centers/Schools were randomly sampled from a list of centers/schools that were expected to provide education and care for children of the target age.
  • Stratifying schools (optional), could take two forms: explicit or implicit stratification
  • Two replacement centers/schools were assigned to each originally selected center/school.


Second stage: Sampling within centers/schools

  • Systematic random sampling with equal probabilities
  • Children randomly selected from lists of all eligible children within sampled centers/schools


General notes

  • Sampling of centers/schools was conducted by the sampling team at IEA Hamburg.
  • Sampling procedures within the center/school were carried out by the national study centers, using the Within-school Sampling Software for Windows (WinW3S) provided by the IEA.
Sample size

Intended, per country

  • 200 centers/schools
  • 15 children in each sampled center/school
  • 3,000 children per country


Achieved, across the three countries

Almost 7,000 children and more than 5,000 parents participated in the study. Almost 6,500 staff questionnaires were completed.

Data collection techniques and instruments

Student Assessments

Direct child assessment

  • A study administrator conducted the assessment with each child individually
    • Using electronic tablets
    • 15 minutes per domain
    • 4 domains conducted on two assessment days
  • Types of questions
    • multiple choice
    • free form
    • short response
    • display stimulus
    • re-usable templates
    • complex dynamic items, interactive on-screen element
  • Achievement items
    • A total of 128 items broken down by 4 domains and 13 sub-domains
    • Items per domain
      • Emergent Literacy: 21 items
      • Emergent Numeracy: 22 items
      • Self-Regulation: 69 items
      • Empathy: 16 items

Indirect assessment: As part of the

  • Parent questionnaire
  • ECEC staff or teacher questionnaire


Contextual information about the household and the child

  • Parent questionnaire
    • Completed either online or on paper
    • 24 questions containing 177 items
    • Time to complete approximately 40 minutes
  • ECEC staff or teacher questionnaire
    • Completed either online or on paper
    • Two sections containing 12 questions and 69 items
    • Time to complete approximately 20 minutes
  • achievement or student test
  • audiovisual materials
  • questionnaire

The assessment instrument and the staff questionnaire were administered in 3 languages, the parent questionnaire in 4 languages:

  • English (ENG, USA): direct assessment, parent and staff questionnaire
  • Estonian (EST): direct assessment, parent and staff questionnaire
  • Russian (EST): direct assessment, parent and staff questionnaire
  • Spanish (USA): parent questionnaire
Translation procedures
  • Source materials for all instruments were developed in English.
  • Two independent translators translated the source material into the target language.
  • These two translations were merged by a third person into a single national version.
  • The translated/adapted versions of the instruments were verified by cApStAn.
Quality control of operations

Measures during data collection

  • National project managers (NPMs) in each participating country responsible for data collection
  • Standardized survey operation procedures: step-by-step documentation of all operational activities provided with manuals
  • Full-scale field test of all instruments and operational procedures (in each participating country)
  • Appointment of a national data manager (NDM) to oversee and implement all data tasks
  • National Quality Assurance Monitoring Program
  • International Quality Assurance Monitoring Program
  • Training of NPMs, center/school coordinators, study administrators, national quality assurance monitors (NQAMs)
  • Provision of software tools for supporting activities
  • Survey activities questionnaire (SAQ) to be completed by NPMs
  • Double data entry for questionnaires
  • Visits to centers/schools by international quality assurance monitors (IQAMs)

Measures during data processing and cleaning

  • Thorough testing of all data cleaning programs with simulated data sets
  • Material receipt database
  • National adaptation database
  • Standardized, iterative four-step cleaning process
    • Documentation and structure check
    • Identification variable (ID) and linkage cleaning
    • Background cleaning (resolving inconsistencies in questionnaire data)
    • Valid range checks
  • Repetition of data cleaning until all data shown to be consistent and comparable
  • Identification of irregularities in data patterns and correction of data errors