SAMPLINGEducational Research Writing

Group 6

•In conducting a study, the researcher

may study every member of a given

population or just representative

sample of that population.

• For various reasons, a study of a

sample of the population is often done

instead of complete enumeration.

•The process of choosing a

representative sample of population is

called

SAMPLING.

Selecting the Study Population

•The information collected in order to answer the

objectives of a study is obtained from

cases/individuals

or objects.

EXAMPLE. In the study of Attitudes of Farmers and

Landowners towards Land Reform. The attitudes

that will be examined are those of farmers and

landowners, and they will most likely be the

source of information. These cases or individuals

are commonly called research subjects or

respondents.

•Once the type of cases to be studied has been

determined, the researcher must decide next how

the cases will be selected. For this purpose, it is

important to distinguish between the total

population and the sample from which the data will

be collected.

•The population is composed of elements, each of

which is a potential case in study. Depending on

the objectives of the study , the available resources

and the available time for the study, a researcher

may decide whether to study all the available

elements or cases in a population or just a sample

from the entire population. The usual practice is to

select and study a small sample of the total

population. This process is called sampling.

The Nature of Sampling (Fraenkel and Wallen, 1996)

•Sampling is the process of choosing a representative

portion of a population or some elements in a population

that will represent the entire population.

•It is assumed that the characteristics of the chosen

elements, called sample, reflect the characteristics of

the entire population. In contrast total enumeration or

census requires the study of all elements in the

population.

In the study of sampling, it is important to distinguish the

following concepts: population, target population,

sampling population, sampling frame and sample.

1. Population refers to the total number of elements

(e.g. items, objects, areas, or individuals) to be

studied.

For example, in the study of Sexual Attitudes and

Practices of Students in Public High Schools in

Province A, all students in public high school in the

province constitute the study of population.

1. Target Population is the population for which

representative information is desired.

2. Sampling Population is the population from which a

sample is actually drawn.

3. Sampling Frame is the list of all elements or

sampling units (e.g. items, persons) in a population.

The sample is drawn from the sampling frame.

4. Population Elements pertains to an item, an object,

an area, or an individual on which data will be taken.

It is considered the unit of study. In the example

above, a student in a public high school is a

population element.

5. Sample refers to an individual, an element or a

group of individuals or elements on which information

is obtained. The sample is drawn from a population to

which research results are generalized.

Why Study a Sample?There are several advantages of studying a sample

rather than the total population. Studying a sample is generally

cheaper, faster, and yields more accurate results than

conducting total enumeration.

It is cheaper. Since a sample is smaller than the entire

population, collection and processing of data, therefore,

costs much less.

It is faster. It is definitely quicker to study fewer individuals or

elements than an entire population.

It is more accurate. Fewer errors are expected in data

collection and processing in a study of a sample than in a

study of the entire population.

It ca yield more comprehensive information. A small

sample can be more thoroughly investigated and can yield

more comprehensive information than a big population.

Basic Types of Sampling

Non-probality Sampling. It is arbitrary (non-

random) and is generally subjective. Data

gatherers choose sample cases, “as they wish”

or “wherever they find them.”

Probality Sampling. It is based on the concept

of random selection, a procedure that assures

that all elements in the population are given an

equal chance of being selected as a sample

unit.