module 3 session 04
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Introduction to Sampling
: Censuses vs.Sample Surveys
Module 3
Session 4
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Session Objectives
Distinguish between censuses and sample surveys
Demonstrate the linkages between censuses and
surveys
Discuss the challenges of conducting censuses and largescale surveys in Uganda
Distinguish between random and non random samples
Identify the types andor sources of errors in censuses
and surveys
Discuss how errors can be minimised in censuses and
surveys
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Reminder of Definitions
Population: totality of all units of interest
Sample: partsubset of the population
Censuses: in!uiries that cover the whole population eg"
Uganda #opulation and $ousing %ensus& %IS& 'MIS& $MIS&()*I%S& etc
Sample surveys are in!uiries that cover partsubset of the
population eg" UD$S& U+$S& +SDS& etc
Sampling Frame: list of distinct and distinguishable units inthe population of interest, beginning step in almost all
random sampling schemes& e"g" numbers written on
households before the census night
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Other Definitions
Defacto census- covers all persons found
within the borders of a particular
territorycountry at a particular point in time-
census night
De.ure census-tallies people according to
their regular or legal residence
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Sampling Frames
Sources 0dministrative records-eg $ospital records
1irth and Death egisters
(% lists
oters register
School registers etc
%onstruct your own
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Disadvantages of various
sources of sampling frames
0dministrative records may not be up to
date
%onstructing your own may be too costlyespecially in large scale surveys
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Role of censuses in ganda
#rovide benchmark data for monitoring&planning and policy formulation eg we needdata for U#' monitoring& poverty monitoring 'lection monitoring esource allocation
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Role of censuses in ganda
!cont."
#rovide small area statistics - basic datadisaggregated to the lowest administrativeunit e"g we use census data to know the
number of people in each village& sub countyand district for planning purposes
Show the actual status of the various
indicators$ealth indicators-mortality& disease
prevalence8ertility trends& population growth rate
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#in$ages bet%een censuses
and sample surveys
Sample surveys can be used as a substitute forcensuses
Sample surveys can be used to supplement
census data Sample surveys can be used to pretest census
materials& procedures and methods %ensuses are used as a basis for surveys
conducted between censuses Sample surveys can be used to monitor census
results
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Challenges of Conducting
Censuses and #arge Scale Sample
Surveys
%hallenges of Surveys and %ensuses Mubiru
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&ypes of Samples
=here two types of samples>
andom and +on random samples
andom samples are those whose
composition is not influenced by the sampler
+on andom samples are those whosecomposition is influenced by the sampler
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'dvantages of Random
Samples
)b.ective and hence inferences based on
them are reliable
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Disadvantages of Random
Samples
%ostly to select
+eed skilled manpower to get a random
sample 8or some surveys& random sampling may not
be the best because the sample may not
provide the re!uired data"
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'dvantages of (on Random
Samples
'asy and cheap to select since selection and
substitution can be done at will
Since they are done at will& the data neededcan be easily obtained
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Disadvantages of (on Random
Samples
Sub.ective and hence inferences based on
them are biased
Sampling errors can not be estimated
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&ypes of )rrors
=here are two types of errors& namely> Sampling errors
+on sampling errors
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Sampling )rrors*+iases
Sampling errors are absent in censuses
=heir causes include>
Use of defective sampling frame Use of defective sampling procedures
Use of an estimation method that does not
correspond to the sampling design
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(on Sampling )rrors
+on sampling errors occur both in censuses
and sample surveys but are more
pronounced in censuses
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Sources of (on sampling
)rrors
Defective sampling frames resulting into
coverage errors Under coverage
)ver coverage
%onceptual problems
#hysical environment
Inade!uacy of enumerators and supervisors
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,o% )rrors can be -inimised
Supervision
=raining
Use of the appropriate estimation method#ublicity of the survey
=esting the survey instruments
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Sampling in the Research
rocess
#roblem)b.ectives$ypothesesMethodology Data Sources =arget population
%ensus or sample@ If sample@ Ahat is the sampling design@
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