Sampling

The Nature of Sampling

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 characteristic of the entire population.

In the study of sampling, it is important to distinguish the following concepts: population, sampling population, sampling frame and sample.

Population, this refers to the total number of elements (e.g. items, objects, areas, or individuals) to be studied. For example: in the study: “ Sexual Attitudes and Practices of Students in Public High School of Province A”. What’s the population?----all student.

Population Element. This pertains to an item, an object, an area, or an individual on which data will be taken. It is considered the unit of study. ---a student

Sampling Population. This is the population from which a sample is actually drawn

Sampling Frame. Is the lists of all the elements or sampling units in a population. The sample is drawn from a sampling frame.

Sample. This 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 the research results are generalized.

Basic Types of Sampling

• Non-probability Sampling is arbitrary and is generally subjective
• Probility Sampling is based on the concept of random selection, a procedure that assures that all elements in the population are given equal chance of being selected as a sample unit

Non-probability Sampling examples

Accidental Sampling. the investigator selects the sample as they become available. Say a researcher want to interview 25 students about their study habits. He may stand by the door of a class room and interview the first 25 student. What’s the bias?

Purposive Sampling. The investigator uses a specific purpose in selecting a sample. Example, a researcher wants to know how grandparents feel about their grandchildren. He may select men and women who are 65 years old and above. Younger grandparents are excluded.

Probability Sampling Procedures

A. Simple Random Sampling is the process of selecting sample cases or subset of sample cases from a population, giving all the sampling unit equal chances of being included as a sample. Best example is “drawing of lots”

B. Systemetic Sampling with Random Start. Is a method of selecting a sample from a population by taking the kth units from an ordered population

Say for a study on “ Risk Behavior of Insulin-Dependent Diabetic Patients Admitted in X Hospital in Bacolod” suppose you wish to draw a sample of 15 insulin-dependent patients from 30 illegible patients (from the hospital record)

Procedure:

Population: 30

Sampling frame: List of names of eligible patients

Sampling unit: an insulin-dependent patient

Step 1: Prepare the list numbered 1 to 30 in alphabetical order

Step2: Determin the Sampling interval (K) by dividing the population by the

number of sample desired 30/15=2

Step3: Select a random Start say number 10

Step 4: from the random start take every second (interval=2) name in the list.

When you reach 30 go backto number one until you have drawn

15 numbers

C. Stratified Random Sampling. Is the process of selecting a random sample from

subgroups or strata into which a populationhas beensubdivided.

Say if I want to conduct a study examining the average annual income of adults in Talisay, by definition, my population is “adults in Talisay” this population includes a number of subgroups( e.g. men, women, retired adults, diabled adults, parent adults and single adults, etc.) These different subgroups may be expected to have different incomes. To get a n accurate picture of the income of adults in Talisay, I will selects a sample that represents the population well. This is by matching the percentage of each group in my sample that I have in my population. Say if 15 p% of the population of adults is retired, I will select a sample in a manner that included 15% retired adult. If 55% of the total population is male, 55% of my sample should be male.

D. Cluster Sampling

· a method of selecting a sample of groups of clusters of elements.

· clusters are usually exclusive sub-populations, which together comprise a population. Each cluster consists of heterogenous elements and each is typical of the population.

· for instance in a school where students in each grade level assigned to a heterogenous rather than homogenous sections, each section is considered a cluster.

· The number of clusters in the population represents the size of the population of clusters, while the number of elements in a cluster is called cluster size.

· The sample clusters can be drawn using simple random sampling or systematic sampling with a random start.

“Attitudes Towards Cheating of College Freshmen In a Private School”

· Population: 100 students divided into 10 heterogenous groups each with 10 members

· Desired Sample Size: 50 students, 5 sample clusters need to be drawn at random

· Sampling Frame: List 10 clusters / groups

· Sampling Unit: One group / cluster with10 members

E. Multistage Sampling

· a method where the selection of sample is accomplished in two or more stages.

· the N is first divided into a number of first stage units from which a sample is drawn. Then, divided further into second stage units. More stages may be added, if desired, by dividing the population into a hierarchy of sampling units corresponding to the different sampling stages.

· This process is usually used when the population in each hierarchy is considered one stage.

• “Men’s Participation in Child Care”

· Population: All the men with 0 to 6 year-old children in the province

· Desired Sample Size: 135 married men with 0 to 6 year-old children in the province

· Sampling Frame: List of men with 0 to 6 year-old children

· Sampling Unit: A man with 0 to 6 year-old children

Research Variables

Research Variables

• a VARIABLE is a concept that stands for a variation within a class of objects or persons (Frenkel and Wallen, 1996)

• a VARIABLE is a characteristic or property that can take different values or attributes (Schutt,1999)

• Variables should be measurable and observable.

Examples of variables:

• age
• sex marital status
• income
• location of business

• revenue
• type of work
• number of meetings
• degree of malnutrition
• level of fertilizer
• type of crop
• size of land

Types of Variables:

Variables can be Classified as: dependent, independent, intervening, and antecedent variables

Dependent Variable: the dependent variable is the “assumed effect” of another variable.

Independent Variable: The Independent Variable is the “assumed cause” of a problem.

Intervening Variable : the factor that works “ between” the independent and dependent variable.

Sample problem: “ Knowledge of the Danger of Smoking, Attitude towards life, and Smoking Habits of Young Professionals"

Antecedent Variable: is a factor or characteristic which is found before (ante) the independent Variable.

Sample problem: “ Attitudes towards Land Reform and Acceptance of the Program Among Lowland Farmers of Northern Luzon"

Operational Definition of Variables

Some researchers cannot answer their research questions because they do not have clear measures of their variables. A variable must be operationally defines according to how it is used in the study so that it can properly be measured.

The operational definition gives a specific meaning to the variable. The definition clarifies how a variable or term be used and measures in the study. A variable must be defined in terms of events/ units of measurement that are observable by the senses ( Fisher, et.al.,1994). These events/units of measurement serve as indicators of the variables.

The operational definition of a variable specifies how a variable or a term is interpreted in the study and also sets the procedure for measuring variable. An operational definition of a variable in one study may differ from that employed in another study.

Study the examples below:

Please note that these definitions are not those that one will find in the dictionary. These definitions are define by the researcher him/herself to fit his/her study.

Establishing Categories of Variables

In some cases, a number, an amount or a sore may not be sufficient to represent a variable. To facilitate a description and analysis of data, categories of variables can be established. Each category should be operationally defined. The categories must be:

1. Mutually exclusive and
2. Exhaustive

MUTAULLY EXCLUSIVE CATEGORIES

Mutually exclusive categories do not overlap. Categories are mutually exclusive when a respondent cannot be assigned to more than one category. Some variables, like the knowledge scores, can be grouped and each group assigned a category, such as, “high level of knowledge, “ “average level of knowledge,” and “low level of knowledge. Each of these level categories should be operationally defined.

Example No.1

If for instance the researcher defines - level of knowledge about cancer- as “ the number of questions about cancer which a respondent answered correctly,” each level of knowledge may be assigned a range of scores.

Assuming that the possible total score is 20, the possible categories could be:

High level of knowledge = scores of 14 to 20

Average level of knowledge = scores of 7 to 13

Low level of knowledge = scores of 0 to 6

In addition, the score limits should be specified, like for purpose of interpretation like the mean score such as:

High level of knowledge = 13.6 - 20

Average level of knowledge = 6.6 - 13.5

Low level of knowledge = 0 - 6.5

Example No.2

For a variable like “residence” if its operational definition is “ geographical characteristics of the area where the respondents permanently reside,” the possible answer may be categorized as ‘rural” and “urban.” The meaning of “urban,” however, may be different in other studies. The operational deifinition depends on how the word is used in the study. The categories may be defined as:

Rural - refers to a place of residence which is located outside the geographical jurisdiction of a city or a town center.

Urban - refers to a place of residence which is located within the city proper or within the town proper of a municipality.

EXHAUSTIVE CATEGORIES

Categories are exhaustive if all the [possible responses are included among the options of responses. The answers given by every respondent can be assigned to a particular category. If a researcher is not sure about the exhaustiveness of the categories identified, he/she should include “ others,” which is the ‘catch all” category. Under this category, responses which cannot be assigned to any of the other categories can be classified.

Example

A list of categories like: Protestant, Catholic, Muslim, and Buddhist” for responses to a question on religion is not exhaustive because Mormon cannot be classified under any of the categories in the list. To correct this the item on the questionnaire should look like this:

What is your religion? Check one : ___Catholic ___Muslim ____Others, specify

___Protestant ___Buddhist

For instance,the variable “hobbies” is operationally defined as “ a type of activity a person engages in during leisure or free time.” The possible categories of this variable may be: “ singing,” “reading,” “painting,” “writing poem,” “sewing,” “others, specify.” What may not be classified under the five specific categories can be classified under “Others.” However, if during data analysis, the number of responses falling under the “others” exceed three, the responses must be specified and based on these an additional category can be added.

Operational Definition of Key Terms

There may be terms in the study (not variables) that have meaning different from their “dictionary meaning” or they take on different meanings, depending on situations or events. These terms must also be defined operationally to avoid misinterpretation. The definition depends on how the word is used and measures.

Examples:

1. Family planning user is any currently married woman aged 15 to 49 years old or married man aged 15 or older who has used a method to prevent or space pregnancy at least once during the last three months.

2. Coastal Barangay is a village or community which is located near the sea where fishing is the main activity of sresidents.

3.Merging is the absorption of one or more business firms by another existing firm which retains its identity and takes over the rights, privileges, franchises, and properties and assumes all the liabilities or obligations of the absorbed firm/s (Pudadera, 2002).

4. Interest rate represents the cost of borrowing money, expressed as a percent rate, for a given period of time.

Review of Related Literature

Review of Related Literature

A review of related literature is the process of collecting, selecting, and reading books, journals, reports, abstracts, and other reference materials. The following information may be collected:

1. Background information about the problem and related concepts.

2. Theories that explain the existence of the problem and the possible connection between certain factors and the problem

3. Data that confirms the existence and seriousness of the problem

4. General and specific findings of studies related to the problem

5. Recommendations for further study given in related studies

Why Review Literature?

A review of related literature is a must in research. The following are some of the obvious reasons;

1. It helps the researcher identify and define a research problem

2. It helps justify the need for studying a problem.

3. It prevents unnecessary duplication of a study

4. It can be a source of a theoretical basis for the study

5. It enables the researcher to learn how to conceptualize a research problem and properly identify and operationally define study variables

6. It helps formulate and refine research instruments

7. It provides lesson for data analysis and interpretation.

When to Start Reviewing Related Literature?

While the research problem is still being conceptualized, the researcher must already start reviewing literature. In identifying and defining the research problem, the researcher must be able to show evidences that the problem really exists and is worth investigating.

It is important that the researcher knows what is already known about the problem or what earlier researchers have found about it and what questions still need to be answered before the research questions or objectives are finalized.

Theories which the researchers use to explain the existence of a research problem and used as bases in analyzing relationships between variables can be generated from reference books on theories or from related studies. The researcher therefore, must have already read adequate literature at the start of the research activity.

What Materials to Review?

1. General References

Examples are indexes, reviews and abstracts

2. Primary Sources

Examples are researches found on published journals.

3. Secondary Sources

Publications where authors cite the works of others. Examples are books, encyclopedias. Secondary sources are good references for overview of the problem.

Steps In Literature Review

1. Review the precise definition of the research problem. Note the key variables specified in the study objectives and hypothesis.
2. Formulate “search terms” (key words or phrases)

Problem: Adolescents’ Perceptions on the Effect of Punishment on Self-Esteem

and Academic Performance”

Search term: “punishment and learning”, “self-esteem and performance”

3. Using indexes of general references, serach for relevant primary and secondary sources guided by the search terms.
4. List in a note of index card the bibliographical data of the pertinent information selected as follows:

a. author

b. title

c. name of publication

d. date of publication (include place and date)

e. pages of the article

5. Read the selected reading materials, take note and summarize key points. Prepare a note card for easy retrieval and classification. In taking note, be as brief as possible but include all relevant information which you can use in your full review, such as : the problem, the objectives, and hypotheses, the major findings, and conclusions.

Review ofRelated Literature

Research Framework

The Theoretical and Conceptual Framework

Research Framework
A problem exists because of certain reasons. Even if the cause or causes of a problem cannot be pinpointed, its existence may be discussed by examining certain patterns that relate to the problem situation. In explaining the existence of a problem, a researcher may base the explanation on a theory. The connection between a theory and the problem is explained in the THEORETICAL FRAMEWORK. The theoretical framework may be further explained and illustrated in concrete terms using the CONCEPTUAL FRAMEWORK.

The Rule of Theory ion Research
A theory is a set of concepts which explains the occurrence of a certain phenomenon. It is a statement of relationship between two variables, one acting as the independent variable , another as the dependent variable.

An independent variable is assumed to be the “cause” of the problem, while the dependent variable is the problem itself or the phenomenon being studied

Since one can never be sure whether a given theory provides the best explanation for a set of observation, it is possible to use two or more competing theories and test which theory best explains the problem. A competing theory may also be used to explain the possible confounding influence of other variables on the assumed relationship between the major variables of the study.

Examples of theories that explain behavior

Dissonance theory. According to Festinger (Wicklund and Brehm, 1976) “ Feelings of tension arises when one becomes aware of two conflicting or inconsistent cognitions. A person is motivated to justify his behavior in order to reduce tension when acting contrary to his attitude.”
This theory can be a bsis for this situation:
A religious man who committed adultery may justify his aaction with “ an experience of a moment of weak ness, “ “ Akoy’ tao lamang—natutkso kong minsan”

Self- Perception theory(Bem,1972, in Myers, 1983). “When one is unsure of his/her attitude, he/she infers it back by looking at the behavior and the circumstances under which occurs. When a person’s attitude is weak, he/she simply observes his/her behavior and its circumstances and simply infers what his/her attitude will be”

This theory can be a bsis for this situation:
Man’s attitude is influenced by his actions. A child abuser may tend to have an indifferentattitude towards children.

Theoretical Framework
A theoretical framework presents a theory that explains why a problem under study exists ( Mercado, 1994), and explains the connection between certain factors and problem. The choice of theory depends on the number and nature of variables and the relationship being examined.

The starting point in developing a theory is to review related literature. A background on theories on behavior, education, communication, sociology and anthropology can be very useful.

Functions of a Theoretical Framework

 It provides general framework which can guide the data analysis
 It identify the variables to be measured
 It explains why one variable can possibly affect another
 It limits the scope of data relevant to the framework by focusing on the variables
 It stipulates the specific frame of mind or viewpoint that the researcher will take in analyzing and interpreting the data.

” Not all research studies need a theoretical framework, but relational and causal studies do.”

Concepual Framework
The conceptual framework is a n elaboration of the theoretical framework in concrete terms. The conceptual framework is anchored on the theoretical framework. The conceptual framework needs to be consistent with and related to the theoretical framework. It specifies the variables of the study and the expected flow of relationship among them.

Based on the theory used and/or related literature, the predicted association between variables or the assumed effect of one variable on the other variableis explained. Arguments on how and why a particular factor can possibly influence another a re presented. Findings of related studies may be used to support the argument.

The conceptual framework explains in detail the:
 Variables to be observed in the study
 Assumend connection between the independent and the depended variables.

The conceptual framework is summarized in a paradigm or schematic diagram identifying the hypothesized link between the independent and dependent variables.



Example:

Research Title: “ The effect of Curfew on the Attitude of Students towards their Studies and their Academic Performance”

Many parents or guardians prevent their children from staying out late at night by imposing curfew, so that they can study or perform well in school. But, many students still perform badly in school, even if they are forced to be home early. Is curfew an effective means of improving students‘ attitude towards their studies and consequently their school performance? Does curfew adversely affect students’ school performance?

Theoretical Framework:
“People value their sense of freedom and like to protect an image of efficacy (Baer, et.al.,1980). When social pressure threatens their sense of freedom, they tend to rebel.” According to the theory of psychological reactance, people act to defend their freedom. Experiments have shown that attempts to restrict a person’s freedom often results in a reactive “boomerang effect.” Restricting someone’s movement is also reducing or taking away one’s freedom. Most people use restriction as a preventive measure. For some it may work , for others, it may not. It may produce good result for others, for some, it may do more harm than good.

Conceptual Framework:
Imposing curfew can be viewed as a form of freedom restriction. When students are prevented from staying out late by their parents, and are expected to be home not later than the specified curfew, young students may view this as a curtailment of freedom. While the parents’ intentions are good, they may be perceived by their children as unjust and unfair and they may harbor ill feelings against their parents and rebel. Instead of coming home early, they may even come home very late and drunk to spite their parents. This rebellion can possibly result to irregular attendance in classes, indifference towards their studies and consequently poor grades.
In this study, exposure or non-exposure to curfew serves as the independent variable, while school performance is the dependent variable. If the effect of curfew is positive, those who will be subjected to curfew is expected to have better grades than those who were not subjected to curfew. On the other hand, a negative effect will be evidenced by poor grades, the diagram below shows the expected floow of relationship between variables.