Disadvantages of Systematic Sampling and Applications of Systematic Sampling

Disadvantages of Systematic Sampling:

·           Effect of Periodicity: When there is hidden periodicity in the population or a cyclical or periodic movement of the data the systematic sample is less representative than the simple random sample.

·           Effect of Trend: When there is a monotonic trend in the population elements, a systematic sample will perform less well.

·           Effect of Ordering: A major limitation of systematic sampling is that unless some assumption is made about the ordering of the list, the variability among the values of the sampled elements does not provide a basis for estimating the variability of the sampling distribution.

Applications of Systematic Sampling:

·           In Gallup Poll: Systematic sampling is a common sampling design in many opinion surveys.

·           In Quality Control: The systematic sampling is extensively used in manufacturing industries for statistical quality control of their products.

·           In Auditing: In auditing accounts to check compliance, the most natural way to take a sample from the list of accounts is systematic sampling.

·           In Market Research: Systematic sampling has its wide applications in market research.

·           In Crop Estimation: In crop yield estimation, systematic sampling has been extensively used.

·           In Health Studies: In recent years, UNICEF and WHO have been extensively used systematic sampling method worldwide in child nutrition, iodine deficiency disorders surveys to assess the prevalence of these diseases.

Read More

Stratified Sampling

Stratified Sampling:

Stratified random sampling is a sampling plan in which the populations is divided into several non-overlapping strata and select a random sample from each stratum in such a way that units within the strata are homogeneous but between strata they are heterogeneous. The sub-populations making up the whole population are called strata.

Principle of Stratification:

The process of stratification involves dividing the population into several sub-populations, which we call strata. In forming such strata, a few principles should be followed to take full advantage of stratified sampling. These are:

• The strata should be non-overlapping and exhaustive so that they together comprise the whole population. Thus several administrative divisions of the country, ecological zones, rural-urban residence and the like may be thought of as different strata. The strata should be made as homogeneous as possible, ensuring greater similarity within the strata than between the strata.
• Strata are to be formed on the basis of some known characteristics of the population, which are believed to have some relationship with the subject of inquiry and variables of interest.
• When stratification with respect to the characteristics under study becomes difficult for practical reasons, administrative convenience may be considered as the basis for forming the strata.
• With a view to improve the sampling design, strata should be formed on the basis of natural characteristics as far as possible.
• Past data, intuition, expert judgment or preliminary findings from pilot surveys may also be used to set-up the strata. This, however, requires that we have prior knowledge of the nature of the population from which we are sampling.

Stratified Sampling:

Stratified random sampling is a sampling plan in which the populations is divided into several non-overlapping strata and select a random sample from each stratum in such a way that units within the strata are homogeneous but between strata they are heterogeneous. The sub-populations making up the whole population are called strata.

Principle of Stratification:

The process of stratification involves dividing the population into several sub-populations, which we call strata. In forming such strata, a few principles should be followed to take full advantage of stratified sampling. These are:

• The strata should be non-overlapping and exhaustive so that they together comprise the whole population. Thus several administrative divisions of the country, ecological zones, rural-urban residence and the like may be thought of as different strata. The strata should be made as homogeneous as possible, ensuring greater similarity within the strata than between the strata.
• Strata are to be formed on the basis of some known characteristics of the population, which are believed to have some relationship with the subject of inquiry and variables of interest.
• When stratification with respect to the characteristics under study becomes difficult for practical reasons, administrative convenience may be considered as the basis for forming the strata.
• With a view to improve the sampling design, strata should be formed on the basis of natural characteristics as far as possible.
• Past data, intuition, expert judgment or preliminary findings from pilot surveys may also be used to set-up the strata. This, however, requires that we have prior knowledge of the nature of the population from which we are sampling.

Stratified Sampling:

Stratified random sampling is a sampling plan in which the populations is divided into several non-overlapping strata and select a random sample from each stratum in such a way that units within the strata are homogeneous but between strata they are heterogeneous. The sub-populations making up the whole population are called strata.

Prin   ciple   of Stratification:

The process of stratification involves dividing the population into several sub-populations, which we call strata. In forming such strata, a few principles should be followed to take full advantage of stratified sampling. These are:

• The strata should be non-overlapping and exhaustive so that they together comprise the whole population. Thus several administrative divisions of the country, ecological zones, rural-urban residence and the like may be thought of as different strata. The strata should be made as homogeneous as possible, ensuring greater similarity within the strata than between the strata.
• Strata are to be formed on the basis of some known characteristics of the population, which are believed to have some relationship with the subject of inquiry and variables of interest.
• When stratification with respect to the characteristics under study becomes difficult for practical reasons, administrative convenience may be considered as the basis for forming t

Read More