CENSUS VS SAMPLINGPROBABILITY & NON-PROABILITY

SAMPLINGSAMPLING & NON-SAMPLING

ERROR

PRESENTED BY:DHIRESH CHAWLA

SUNIL CHICHRAVIVEK PANDEY

WHEN DATA IS TO BE COLLECTED FROM EACH MEMBER OF THE POPULATION, IT IS KNOWN AS

CENSUS SURVEY

WHEN DATA IS TO BE COLLECTED ONLY FROM SOME MEMBERS OF THE

POPULATION, IT IS KNOWN AS SAMPLE SURVEY

Sampling Method Advantage over Census Method Speed: Less Time Economy : Less Expensive Adaptability Scientific Approach : More Dependable, Less

Manpower, Less Administrative Control

Census Method Advantage over Sampling Method Gives Exact & Accurate results

Sampling used in infinite cases while Census can’t measure or studiedEx : Inspection of Bombs

Test on Quality of Apples In those Census Destroyed all itself

Census were Complete Enumeration while Sampling were Partial Enumeration

Pros n Cons Of CENSUS Method

• True Measure• Benchmark data obtained

for future studies• Detailed information for

sub-groups

• Higher costs• Long time to collect & process

• Difficult to enumerate

Pros n Cons of SAMPLING Method

Low CostLess TimeRepresentative Average results

Not representative total populationNot suitable for producing benchmark data

Probability SamplingAlso known as Random SamplingRandomly selection of samplesIn this probability can be accurately

determinedIncludes :

Simple Random SamplingSystematic Random Sampling

2nd sample are taken at Interval

Stratified Random SamplingRelevant subgroups created

Simple

Systematic

Stratified

Non-Probability Sampling

Also known as Non-Random SamplingSelection is non-random & probability of their

selection cannot be determinedIncludes :

Convenience SamplingBased on ease of access

Purposive SamplingBased on what researcher think

Quota SamplingBased by defined quotas

Volunteer SamplingInternet based opinion survey

Advantages & DisadvantageProbability Sampling

ReliableEasy estimation of errors

Costly to selectNeed skilled Manpower

Sample may not provide required data in some cases

Advantages & DisadvantagesNon- Probability Sampling

Easy & cheap to selectData easily obtainedUnderstood easily

Sampling errors can’t estimatedVariability Can’t Measured or controlled

Sampling Error

Error caused by the act of taking a sampleThey cause sample results to be different from the results of censusDifferences between the sample and the population that exist only because of the observations that happened to be selected for the sampleStatistical Errors are sample error

Causes :

Faulty Selection Of Sample Substitution Faulty Demarcation of sampling units

Two types of error 1. Biased error2. Unbiased error

Non - Sampling Errors

Arises from other types of errors than from a sample

Ex: Tabulation errors

Occur at every stage at the planning or execution of census or sample survey

Also Call as Systematic Error

Not controlled by sample size

Arises From :

Lack of Trained & experienced Investigators

Errors committed during presentation Duplication of units Defective frames & faulty selection of

samples units Lack of adequate inspection &

supervision of primary staff Errors in data processing operation like

as coding, tabulation etc.