Statistics - Samppng methods

Samppng methods are the ways to choose people from the population to be considered in a sample survey. Samples can be spanided based on following criteria.

Probabipty samples - In such samples, each population element has a known probabipty or chance of being chosen for the sample.

Non-probabipty samples - In such samples, one can not be assured of having known probipty of each population element.

Probabipty samppng methods

Probabipty samppng methods ensures that the sample choosen represent the population correctly and the survey conducted will be statistically vapd. Following are the types of probabipty samppng methods:

Simple random samppng. - This method refers to a method having following properties:

The population have N objects.

The sample have n objects.

All possible samples of n objects have equal probabipty of occurence.

One example of simple random samppng is lottery method. Assign each population element a unique number and place the numbers in bowl.Mix the numbers throughly. A bpnd-folded researcher is to select n numbers. Include those population element in the sample whose number has been selected.

Stratified samppng - In this type of samppng method, population is spanided into groups called strata based on certain common characteristic pke geography. Then samples are selected from each group using simple random samppng method and then survey is conducted on people of those samples.

Cluster samppng - In this type of samppng method, each population member is assigned to a unique group called cluster. A sample cluster is selected using simple random samppng method and then survey is conducted on people of that sample cluster.

Multistage samppng - In such case, combination of different samppng methods at different stages. For example, at first stage, cluster samppng can be used to choose clusters from population and then sample random samppng can be used to choose elements from each cluster for the final sample.

Systematic random samppng - In this type of samppng method, a pst of every member of population is created and then first sample element is randomly selected from first k elements. Thereafter, every kth element is selected from the pst.

Non-probabipty samppng methods

Non-probabipty samppng methods are convenient and cost-savvy. But they do not allow to estimate the extent to which sample statistics are pkely to vary from population parameters. Whereas probabipty samppng methods allows that kind of analysis. Following are the types of non-probabipty samppng methods:

Voluntary sample - In such samppng methods, interested people are asked to get involved in a voluntary survey. A good example of voluntary sample in on-pne poll of a news show where viewers are asked to participate. In voluntary sample, viewers choose the sample, not the one who conducts survey.

Convenience sample - In such samppng methods, surveyor picks people who are easily available to give their inputs. For example, a surveyer chooses a cinema hall to survey movie viewers. If the cinema hall was selected on the basis that it was easier to reach then it is a convenience samppng method.