Sample Survey

A sample survey is another source of demographic data carried out in a scientifically selected area which covers only a section or portion (sample) of the population under consideration. A sample survey can be defined as " the process of collecting, compiling, evaluating and publishing of demographic, social and economic data about the sample population at a specified time." Living Standards Survey, Demographic Health Survey, Contraceptives Prevalence

Survey, Fertility and Family Planning Survey etc. are the some example of sample survey.

Population data are collected from a sample of the population which may be representative of the whole population. In a census where cenus is not conducted, population data are collected through sample survey and some estimates are made of its size, growth, structure and characteristic. Even in countries where regular census operation are conducted, the need for collection of population data through sample survey is felt, for a census is taken in most countries only once in ten years. This is very important in the sense that census is taken in each decade, and of course there will be so many things that will happen between the periods.

Sample Surveys was started from later half of nineteenth century from Britain and its uses get accelerated after 1950s. In 1956 Proncenton University had established population research centre and conducted around 400 sample survey on knowledge, attitude and practices related to population for the first time. Now it is the most popular method of data collection in the world.

With the help of trained interviewrs and carefully prepared questionnaires, some special aspects of the population can be studied in depth. For example, information on abortions, contraception, etc, so essential for the study of fertility, can never be obtained from a census, but only through special sample surveys. The quality of data obtained through sample surveys is better than that obtained from a census because they are collected by a comparatively small number of well-trained interviewrs. However, sample survey can never take the place of a cenus or vital registrations.

Generally, Sample Surveys are of following two types:

* Longitudinal Sample Surveys: Surveys are conducted in multiple rounds within the time interval.

* Cross Sectional Sample Surveys: Surveys is conducted in single round.

Advantages Of a Sample Surveys

* Demographic and socio-economic changes between the two census.

* Effectiveness of a program after a certain period of time, ie; family planning services, unmet need in regards to FP services etc.

* Affordable cost in comparison to cenus method.

* Detailed information in a particular area of study.

Limitation/ Drawbacks of Sample Surveys

* There will be a problem of producing data if experts are not available as it requires well-trained experts for questionnaires preparations, sample selection, collections and analysis of data and information.

* Data may not be representative of the total population, particularly where the sample size is small. 

* Often not suitable for producing benchmark data.

* As data are collected from a subset of units and inferences made about the whole population, the data are subject to 'sampling' error.