Sampling

Eulogio “Amang” Rodriguez Institute of Science and Technology
Nagtahan, Sampaloc, Manila
College of Education

Doctor of Education
Major: EDUCATIONAL MANAGEMENT

Subject: Seminar in Project Development, Industrial Planning Design, Implementation and Evaluation
Professor: Dr. Elidio T. Acibar
Reporter: Evelyn L. Embate
Topic: Sampling

SAMPLING
Measuring a small portion of something and then making a general statement about the whole thing.
Advantages of sampling
Sampling makes possible the study of a large, heterogeneous population
It is almost impossible to reach the whole population to be studied. Thus, sampling makes possible this kind of study because in sampling only a small portion of the population may be involved in the study, enabling the researcher to reach all through this small portion of the population. * Sampling is for economy
A research without sampling may be too costly. For an instance if you are to take the whole population, it will take you an expensive cost because of the number of questionnaire copies. * Sampling is for speed
A research without sampling might be too time consuming. If a research takes a long time to finish, there may be many intervening factors that deter the researcher from finishing his research. * Sampling is for accuracy
A time too long to cover the whole study population, may ne inaccurate. By the time the last person is interviewed, the data gathered from the first interviewees may be obsolete already so that the conclusions are no longer accurate. It is important that the research must be finished within a reasonable period of time so that the data are still true, valid, and reliable.
Sampling saves the sources of data from being all consumed
The act of gathering data may consume all the sources of information without sampling.

Sampling Concepts and Terminology * Element
The unit about which information is collected and which provides the basis of analysis. They are the members of the population. These are the certain types of people, families, social clubs. * Population
The theoretically specific aggregation of the elements. Also called universe. The term population includes ALL. * Study population
The aggregation of elements from which the sample is actually selected. This term includes ONLY the selected subjects. This is often defined in the scope and delimitation section of a thesis report. * Sample
These are the elements (people) who are actually selected to participate or to be the subject in the study. * Sampling unit
It is the element or set of elements considered for selection in some stage of sampling. * Sampling frame
It is the actual list of sampling units from which the sample, or some stage of the sample, is selected. * Observation unit
Unit of data collection is an element or aggregation of elements from which information is collected.
It is the actual respondents to a study, the observation units or respondents are the people who are interviewed or who are requested to accomplish questionnaires for data collection. * Variable
A set of exclusive attributes, such as sex, age, employment status. A variable must possess variation. * Parameter
A summary description of a given variable in a population. * Statistics
Summary description of a given variable in a sample. Sample statistics are used to make estimates of population parameters. * Sampling error
The degree of error of a sample statistics when compared with the population parameter. * Representative sampling
A sample will be representative of the population from which It is selected if the aggregate characteristics of the sample closely approximate those same aggregate characteristics in the population. * Confidence level
The degree of confidence that a sample statistics will accurately fall within a certain or specified interval from the population parameter

Principle of sampling 1. Appraisals that involve sampling are Estimates and predictions only 2. Estimates based on sampling are the least accurate when the sample is a small portion of the whole and when the sample is not representative. Conversely estimations based on proportionately large samples and on representative samples are most accurate. 3. Sampling may be categorical or temporal. Categorical is taken proportionally from categories or groups. Sampling is temporal when the sample is in terms of time

Disadvantages of sampling 1. If sampling is biased, or not representative, or too small, the conclusion may not be valid and reliable. 2. In research, the respondents to a study must have a common characteristic which is the basis of the study. If some of the sample do not have this common characteristic, the conclusion become faulty. 3. If the population is very large and there are many sections and subsections, the sampling procedure becomes very complicated. 4. If the researcher does not possess the necessary skill and technical knowhow in sampling procedure, the sampling may become biased and unrepresentative.

General types of sampling
There are two general types of sampling 1. Probability 2. Non-probability
Probability sampling is the proportion of the population and such sample is selected from the population by means of some systematic way in which every element of the population has a chance of being included in the sample.
Non-probability sampling the sample is not a proportion of the population and there is no system in selecting the sample. The selection depends upon the situation.

Types of NON-PROBABILITY SAMPLING 1. Accidental sampling
In this type of sampling, there is no system of selection but only those whom the researcher or interviewer meet by chance are included in the sample.
The problem with this type of sampling is its lack of representativeness. The sample might be a biased one.
In research, every section of the population being studied must be proportionally represented in the sample.

2. Quota sampling
In this type of sampling, specified numbers of persons of certain types are included in the sample. Advantage of quota sampling over accidental sampling is that many sectors of the population are represented. However, its representativeness is doubtful because there is no proportional representation and there are no guidelines in the selection of the respondents. Another danger is that the perception of the minority may become typical in the findings.

3. Convenience sampling
Is the process of picking out people in the most convenient and fastest way to immediately get their reactions to a certain hot and controversial issue. This type of sampling is certainly biased and not representative considering that the people who have telephone are a class by themselves and so their views cannot be considered as views of the people.