1. General Concepts on Sampling Frames
Mukesh K Srivastava
FAO Statistics Division

2. Concepts Target population Population units
all the items (people, farms, animals, businesses, etc.) about which information is needed
Population units
- elements of the target population
Sampling units
well-defined units that allow access to the target population
units of observation

3. Frame
List of all possible units in the population e.g. list of holdings
Listing operation precedes the survey
Many other sources could be used to build the list
population census
business registers/ tax and subsidy registers
land owner register....
Building and maintaining frame could be costly
Unbiased: De Facto not De Jure
Exhaustive and Mutually exclusive
e.g livestock (owner and care taker)
Operational definition of the Statistical Units is needed (Criteria)
Clear concepts and approaches

4. Types of Frames List Frames Area Frames Multiple Frames (combination)
Master Sampling Frame:
Multi-purpose
Multi characteristics

5. Considerations for choosing a Frame
Long term view of all possible surveys
Based upon available infrastructure
Possibility of updating
Statistical Registers: a type of Frame
difficult to keep them updated, if not linked to an administrative process

6. Area Frame Land is divided in segments on the basis of land use
A unique ID is assigned to each segment
List of segments
Segments (or blocks) are Stratified
(Stratum: a group of homogeneous units)
Area Frame: linking of segment with the holding is possible

7. NASS, USDA Area Frame
How is it constructed?
using… satellite imagery digital maps GIS software aerial photography
divide land area into strata based on land use & likelihood of finding agriculture
subdivide land use strata into strata blocks
select a sample of strata blocks
subdivide selected strata blocks into segments

8. NASS Area Frame >50% cultivated 15-50% cultivated
agri urban
commercial
non agricultural
water

9. Area Frame Strengths: complete coverage reduced non-sampling errors
estimates well for commonly produced commodities
versatility
longevity (desertification/ greening)

10. Area Frames Weaknesses:
expensive (frame construction & data collection)
difficult to target specific or rare commodities
sensitive to outliers
can be inefficient
requires definable physical boundaries

11. List Frames Strengths: Weaknesses:
can use inexpensive data collection methods (mail, telephone)
can target specific or rare commodities
can reduce variability due to sampling
cost-efficient: could be built on available resources
Weaknesses:
X does not cover entire population (threshold criteria)
X goes out-of-date quickly
X increased non-sampling errors due to data collection methods
X requires on-going maintenance
build
update
remove duplication
remove out-of-scope records

12. The Choice Depends upon related on going activities in other sectors
Resource availability
Nature of agriculture
Extensive, mono-crop, or
Intensive multi-crop
Scope of surveys
just the crop area, crop monitoring, land degradation or
many economic characteristics e.g. fertilizers, cost of production

13. Conclusion Statistics Dedicated technical session References
public good
costs and has value
Master sampling frame (private sectors activities)
Dedicated technical session
References
Multiple Frame Agricultural Surveys (FAO)
SDS 7
SDS 10

14. Shukran Jazeelan.