1st nrc meeting, 16-19 october 2006, amsterdam 1 sampling: next steps
TRANSCRIPT
1 1st NRC Meeting, 16-19 October 2006, Amsterdam
Sampling: Next Steps
2 1st NRC Meeting, 16-19 October 2006, Amsterdam
Overview
Sampling responsiblilites
Your next tasks as NRCs
Preparations for school sample selection
Time lines
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Sample Selection in ICCS
Goal for sample selection in ICCS:
Selecting a sample of students and teachers that
represents the situation in your country well.
meets the IEA standards for sampling precision.
meets your research interests.
Needed: Adaptation of the international sampling design to the situation in your country.
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Sampling Responsibilities
Sampling referee (Jean Dumais) :– Advise on sampling methodolgy
– Review sampling execution
– Resolve possible conflicts
IEA Data Processing Center – Provide a sampling preparation manual
– Review national sampling plans
– Select school samples
– Provide within-school sampling software
– Compute sampling weights
5 1st NRC Meeting, 16-19 October 2006, Amsterdam
Sampling Responsibilities: NRCs
NRCs:– Provide basic information about school
system
– Develop national sampling plan
– Provide a school sampling frame
– Review and approve school sample
– Perform within-school sampling
6 1st NRC Meeting, 16-19 October 2006, Amsterdam
Basic Information
Target population– Which grade in your country corresponds to
the international desired target population definition?
Organization of school system– Schools
– Classrooms
– Teachers
NRC task: provide basic information about school system to DPC.
7 1st NRC Meeting, 16-19 October 2006, Amsterdam
Coverage
Some countries may have reduced population coverage.– Example: Language groups– Example: Geographical regions
Limitations in national coverage will be annotated in the IEA publications.
NRCs are strongly encouraged to provide full national coverage.
NRC task: define categories for reduced coverage.
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Exclusions
Some parts of the target population may have to be excluded.– Example: special education schools
– Example: very small schools
Student exclusion rate must be below 5%.
NRC task: define categories for reduced coverage and exclusion.
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Stratification
Stratification: dividing the population into non-overlapping subpopulations prior to sample selection.
Purposes:– Increase precision of survey estimates– Ensure proportional representation
Examples of stratification variables:– Regions (states, provinces…)– School types (public, private...)
NRC task: define stratification variables.
10 1st NRC Meeting, 16-19 October 2006, Amsterdam
National Options
National Options– Example: Over-sampling in some strata
– Example: Testing additional populations
Larger sample may be needed– Reason: previous surveys showed large
clustering effects in some countries.
Result: NRC and DPC agree on national sampling plan.
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School Sampling Frame
A comprehensive list of ICCS-eligible schools.
Must contain:– School identification number.
– Measure of size (students in grade 8).
Should contain:– Number of grade 8 classes.
– School name.
– Address information.
NRC task: provide sampling frame to DPC.
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Example of a Sampling Frame
No merged cells, no sub-totals
A stratification variable is included
Exactly one Excel worksheet
Variable description in EnglishKey variables are included
Each school represented by exactly one entry in one row
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DPC Task: Selection of School Sample(s)
Option 1: Selecting a FT sample in 2007 and an MS sample in 2008.– Convenience sample for the FT is possible.– Recent changes in school system can be taken
into account.
Option 2: Selecting a MS and a FT sample simultaneously in 2007.– No overlap between FT and MS schools– Inferences are possible– Standard in IEA surveys
Second option is the preferred one.
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Sampling Time Lines
January 2007: Agreement on all national sampling plans.
March 2007: All school sampling frames finalized.
June 2007: All FT and MS school samples selected and approved.
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???must we cover this???
Within-school sampling??
Participation rates??
Weighting??
Standard error estimation??
16 1st NRC Meeting, 16-19 October 2006, Amsterdam
Country Consultations
During this meeting, individual country consultations between you and the DPC staff will be held.
We would like to talk with each of you!
Please sign up!
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Thank you!
Contact: Olaf Zuehlke
Sabine Meinck
Email: [email protected]
Telephone: +49/40/48 500 750
Fax: +49/40/48 500 501