Sampling Frames and
Sample Design
Pres. 5
United Nations Regional Workshop on the 2010 World Programme on Population and Housing Censuses:
Census Evaluation and Post Enumeration Surveys, Addis Ababa, Ethiopia, 14-18 September 2009
Sample Frames & Sample Design
Frames: Material from which a sample is drawn
Each unit to be included in the universe
There should be no duplicates
Each unit should be well defined and distinguishable
from other units (it should be unique)
Should be updated
For PES first stage units Primary Sampling Units
(PSUs), in many countries area clusters
United Nations Regional Workshop on the 2010 World Programme on Population and Housing Censuses:
Census Evaluation and Post Enumeration Surveys, Addis Ababa, Ethiopia, 14-18 September 2009
Choices of PSUs
 Must have clearly identifiable and stable boundaries
 Must completely cover the relevant population
 Preferably must have measures of size
 They should be mapped
 Must cover the whole country
 The number of PSUs must be relatively large
United Nations Regional Workshop on the 2010 World Programme on Population and Housing Censuses:
Census Evaluation and Post Enumeration Surveys, Addis Ababa, Ethiopia, 14-18 September 2009
Common problems with EAs
 Incomplete coverage
 Inadequate maps
 Poor measures of size or lack of them
United Nations Regional Workshop on the 2010 World Programme on Population and Housing Censuses:
Census Evaluation and Post Enumeration Surveys, Addis Ababa, Ethiopia, 14-18 September 2009
Sampling Strategies
 Probability household surveys
 It is usual to make inferences in a PES for a number of
analytical domains
 Relatively large samples necessary in each domain for
reliable estimates
 Stratified cluster sample design-common
 First-stage units–area clusters/EAs
 PPS systematic sample selection
 Second-stage, common to canvass all persons in selected
households
United Nations Regional Workshop on the 2010 World Programme on Population and Housing Censuses:
Census Evaluation and Post Enumeration Surveys, Addis Ababa, Ethiopia, 14-18 September 2009
Multi-stage Cluster Sampling
 Usually used when sampling hierarchical populations
 e.g. persons within households which can be selected from
EAs
 The hierarchical levels are called stages
 First stage units are called primary sampling units (PSUs)
e.g. EAs
 Second stage units are called secondary sampling units
(SSUs) e.g. households
 Last stage units are called ultimate sampling units (USUs)
e.g. persons
United Nations Regional Workshop on the 2010 World Programme on Population and Housing Censuses:
Census Evaluation and Post Enumeration Surveys, Addis Ababa, Ethiopia, 14-18 September 2009
Why Area sampling?
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At national level only a frame of EAs is required
Data collection is more efficient
Lower costs compared to simple random sampling (SRS)
Supervision is easier
However, estimates are prone to higher variability
compared to SRS
United Nations Regional Workshop on the 2010 World Programme on Population and Housing Censuses:
Census Evaluation and Post Enumeration Surveys, Addis Ababa, Ethiopia, 14-18 September 2009
Importance of Stratification
 Population subdivided into heterogeneous groups that are
internally homogenous
 Stratification based on variables correlated with the extent
of coverage-geopolitical subdivisions
 Internal homogeneity can be maintained with regard to
socio-demographic variables e.g. urban stratum
 Common strata may include: rural, urban, provinces etc.
United Nations Regional Workshop on the 2010 World Programme on Population and Housing Censuses:
Census Evaluation and Post Enumeration Surveys, Addis Ababa, Ethiopia, 14-18 September 2009
PES sample design
 A single-stage stratified clustered sample design is
commonly adopted
 When the PSUs i.e. EAs are selected all households in
selected EAs are canvassed
 This is necessary because they have to be matched with
the census population
United Nations Regional Workshop on the 2010 World Programme on Population and Housing Censuses:
Census Evaluation and Post Enumeration Surveys, Addis Ababa, Ethiopia, 14-18 September 2009
PES sample selection
 First stage units selected are PSUs (EAs)
 At the next stage all households in selected EAs are
included in the sample
United Nations Regional Workshop on the 2010 World Programme on Population and Housing Censuses:
Census Evaluation and Post Enumeration Surveys, Addis Ababa, Ethiopia, 14-18 September 2009
Sample Size
Sample size depends on estimate requirements
Geographic level (national, province, urban/rural)
Demographic (sex, age)
Reliability
Confidence level
United Nations Regional Workshop on the 2010 World Programme on Population and Housing Censuses:
Census Evaluation and Post Enumeration Surveys, Addis Ababa, Ethiopia, 14-18 September 2009
Sample Size
 To estimate sample size in the case of proportions you
must:
 Know the occurrence of the event in the population
 Specify a confidence interval
 Specify the margin of error or precision
 To estimate percentage of households with access to
family planning services about 55%; confidence interval
for a standard error of 2 %
pq
55 x 45
n


 619
 The sample size works out to be: h ( sd ) 2
4
United Nations Regional Workshop on the 2010 World Programme on Population and Housing Censuses:
Census Evaluation and Post Enumeration Surveys, Addis Ababa, Ethiopia, 14-18 September 2009
Sample Size
 Adjusting for non-response, e.g. 10%:
619
 688
0.90
 Adjusting for the design effect for a complex sample
design
 Design effect of 2 is a default value : 2 x 688 =1,376
 This may apply to each province (analysis) domains. If they
are five provinces
 Sample size will be 5 x 1, 376 = 6,880
United Nations Regional Workshop on the 2010 World Programme on Population and Housing Censuses:
Census Evaluation and Post Enumeration Surveys, Addis Ababa, Ethiopia, 14-18 September 2009
Sample Size
United Nations Regional Workshop on the 2010 World Programme on Population and Housing Censuses:
Census Evaluation and Post Enumeration Surveys, Addis Ababa, Ethiopia, 14-18 September 2009
Sample Size
United Nations Regional Workshop on the 2010 World Programme on Population and Housing Censuses:
Census Evaluation and Post Enumeration Surveys, Addis Ababa, Ethiopia, 14-18 September 2009
Sample Size
United Nations Regional Workshop on the 2010 World Programme on Population and Housing Censuses:
Census Evaluation and Post Enumeration Surveys, Addis Ababa, Ethiopia, 14-18 September 2009
Thank You!
United Nations Regional Workshop on the 2010 World Programme on Population and Housing Censuses:
Census Evaluation and Post Enumeration Surveys, Addis Ababa, Ethiopia, 14-18 September 2009