Category: Research Designs

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Sampling.ppt

1. Simple Random Sampling

Individuals are chosen in such a way that each has an equal chance of being selected, and each choice is independent of any other choice. If we wished to draw a sample of 50 individuals from a population of 600 students enrolled in a school, we could place the 600 names in a container, and, blindfolded, draw one name at a time until the sample of 50 was selected. However, this process is cumbersome (burdensome) and is rarely used. A more convenient way of selecting a random sample, so that the individuals can be equated, is by the use of a “table of random numbers.” When a table is used, it is necessary to assign consecutive numbers to each member of the population (from which the sample is to be selected). Then, entering the table at any page, row, or column, the researcher can select the sample from 001 to 999 (three digits); and from 0001 to 9999 (four digits). When a duplicated number or a number larger than the population size is encountered, it is skipped and the process continues until the desired sample size is selected.

*Ask me to demonstrate when you are in your expert group…!!!

2. Systematic Sampling

Consists of the selection of each nth term from a list. For example, if a sample of 200 were to be selected from a telephone directory with 200,000 listings, one would select the first name by selecting a randomly selected name from a randomly selected page. Then every thousandth name would be selected (200,000/200=1000^th) until the sample of 200 names was complete. If the last page were reached before the desired sample size had been selected, the count would continue from the first page of the directory. Systematic sampling, sometimes called interval sampling, means that there is a gap, or interval, between each selection. This method is often used in industry, where an item is selected for testing from a production line (say, every fifteen minutes) to ensure that machines and equipment are working to specification. Alternatively, the manufacturer might decide to select every 20th item on a production line to test for defects and quality. This technique requires the first item to be selected at random as a starting point for testing and, thereafter, every 20th item is chosen. This technique could also be used when questioning people in a sample survey. A market researcher might select every 10th person who enters a particular store, after selecting a person at random as a starting point; or interview occupants of every 5th house in a street, after selecting a house at random as a starting point. It may be that a researcher wants to select a fixed size sample. In this case, it is first necessary to know the whole population size from which the sample is being selected. The appropriate sampling interval, I, is then calculated by dividing population size, N, by required sample size, n, as follows: I = N/n

3. Stratified Random Sampling

This is possible when the population is subdivided into smaller homogeneous groups, called strata (to get more accurate representation). For example, in an income study of wage earners in a community, a true sample would approximate the same relative number from each socioeconomic level of the whole community. If, in the community the proportion were 15% professional workers, 10% managers, 20% skilled workers, and 55% unskilled workers, the sample should include approximately the same proportions in order to be considered representative. Within each subgroup, a random selection should be used. Thus, for a sample of 100, the researcher would randomly select 15 professional workers from the subpopulation of all professional workers in the community, 10 managers from that subpopulation, and so on. This process gives the researcher a more representative sample than one selected from the entire community, which might be disproportionately weighted by a predominance of unskilled workers. In addition to socioeconomic status, such characteristics as age, sex, extent of formal education, racial origin, religious or political affiliation, or rural-urban residence might provide a basis for choosing a stratified sample (strata).

4. Area or Cluster Sampling

It is sometimes expensive to spread your sample across the population as a whole. For example, travel can become expensive if you are using interviewers to travel between people spread all over the country. To reduce costs you may choose a cluster sampling technique. This sampling technique is appropriate when, a) the population of interest isinfinite, b) when a list of members of the population does not exist, or, c) when the geographic distribution of the individuals is widely scattered. Let’s say we want to select a sample of all public school elementary teachers in the five largest cities in Thailand(Bangkok, Nakhon Ratchasima, Nonthaburi, Chiang Mai, and Songkhla). A simple random sample would be impractical. From the 5 largest cities, three could be selected. From these three cities, all public elementary schools could be listed and a random sample of 30 (10 from each city) can be selected. From these 30 schools, we can then randomly select 5 teachers in each school. So, our true sample will be – 30 x 5 = 150 elementary school teachers.

Non-probability Sampling

› Those that use whatever subjects are available, rather than following a specific subject selection process

› May produce samples that do not accurately reflect the characteristics of a population

› May lead to unjustifiable generalization and should not be used if random selection is practicable

› Educational researchers, because of administrative limitations in randomly selecting and assigning individuals for a research, often use available classes as samples (e.g.: psychology professor uses students from Introduction to Psychology class as subjects – the results of this study can be generalized only to other similar groups of psychology students)

› So, this kind of sampling may restrict generalizations (generalizable only to similar population)

› Sample made up of volunteers may represent biased sample – volunteers may not necessarily be representative of a total population

1. Convenience sampling– selection based on the availability of subjects (whomever happens to be available at the time); also known as accidental sampling or haphazard sampling; sampling bias can occur

› Volunteers

› Pre-existing groups

2. Purposive sampling– selection based on the researcher’s experience and knowledge of the group being sampled; also known as judgment sampling; researcher believes a particular sample is appropriate for his/her study

› Need for clear criteria for describing and defending the sample

› Experience and prior knowledge of the researcher about a particular group (to be used as sample) are essential

› The researcher can be “wrong”

3. Quota sampling– selection based on the exact characteristics and quotas of subjects in the sample when it is impossible to list all members of the population (e.g.: an interviewer might be told to go out and select 20 adult men and 20 adult women, 10 teenage girls and 10 teenage boys so that they could interview them about their television viewing)

› Data gatherers are given exact characteristics and quotas of persons to be interviewed (e.g.: 35 working women with children under the age of 16, 20 working women with no children under the age of 16, etc.)

› Data are obtained from easily accessible individuals

› Thus, people who are less accessible (more difficult to contact, more reluctant to participate, and so forth) are underrepresented

Qualititative Sampling

Because of the unique characteristics of qualitative research, both random and non-random sampling techniques cannot be used. This calls for alternative sampling strategies for qualitative research.

› In-depth inquiry

› Immersion in the setting

› Importance of context

› Appreciation of participant’s perspectives

› Description of a single setting

A qualitative researcher relies on his/her experience and insight to select participants. There are several types of sampling techniques possible for a qualitative study:

1. Intensity sampling= compare differences of two or more levels (“extremes”) of the research topic; e.g.: good vs. poor students (two extremes); effective vs. ineffective teachers (two extremes); small vs. medium vs. large size classes (three extremes), experienced vs. inexperienced teachers, etc.
2. HomogeneousSampling = Subjects chosen by similarity based on a given characteristic
3. CriterionSampling = Selection of all cases that meet a certain standard
4. SnowballSampling = Selection of subjects who identify other subjects; one subject gives the researcher the name of another subject, who in turn provides the name of a third, and so on (e.g.: drug dealers, criminals, gay, isolated, etc.)
5. Random PurposiveSampling = From a purposive sample too large for a study, a random selection is performed

Sample Size?

› Time

› Money

› Access

› Complexity of data analysis

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[vc_row][vc_column][vc_column_text]Writing a research proposal requires specialized skills and attention to intricate details. Neglect in these areas can result in the presentation of a paper that lacks quality and technical soundness (from a research viewpoint). One can find many tips to improve proposal writing from research textbooks and myriad of website articles. However, there is one thing that I personally would like to emphasize and encourage researchers to remember:

A researcher should consider the possible questions readers might have (if they had to read and examine the proposal) and answer all these questions, as accurately and comprehensively as possible. Anticipating the doubts others might have about the research framework allows a researcher to touch base with all aspects of an investigation prior to executing the actual plan.

The following is a format for writing a research proposal (explanation for each sub-heading is given for clarity):

CHAPTER 1

INTRODUCTION
You start off by giving readers a general idea about your topic. Be brief. Your introduction should be engaging and stimulating in a way that readers will be interested and attracted to read further. A lengthy introduction might result in unfavorable ‘first impression’. Do not use factual statements (as yet). Avoid references at this juncture. Write the introduction in your own words. Imagine you are starting a conversation with someone and you desire to keep the one listening to you attentive all through.

Background of the Study – Present the motivation for doing the research. Indicate what made you become interested in the topic in the first place. Is the topic directly related to you? Or is it a phenomenon that you observed to be prevalent in your surrounding? Why are you driven to investigate and study the topic?

Statement of the Problem – This is where you explain your topic. You will recall that in the title page, your statement of the topic is very brief and non-explanatory. So, this is where you get to expound on your topic. You can narrow the area of investigation by pointing out your concerns and focus in the research. For example, you can write, “For the purpose of this research, the researcher will investigate the effects of extrinsic motivation on math performance of third graders…” Here, the researcher is narrowing down the construct – motivation – to ‘extrinsic motivation’…this means that the researcher is not interested in studying the effects of intrinsic motivation on math performance. You can also state the variables (dependent and independent variables) involved in the study under this section. Many scholars say that ‘Statement of the Problem’ is the HEART of any research proposal. So, make sure that you are specific, concise, and distinctive in elaborating the topic under investigation.

Purpose of the Study (Objectives of the Study) – What is to be accomplished by the research? What is your research going to accomplish that other researches didn’t accomplish? These objectives are specific aims of the research, often broken down according to what is to be accomplished into smaller logical components. In other words, specific objectives relate to the specific research question/hypothesis the investigator wants to answer through a proposed study. It is advisable to work on a few specific objectives; an average of three and a maximum of five are appropriate. E.g., The study will ascertain/measure the degree and direction of relationship between variable A and variable B; The study will examine and describe and the type of attitude male prisoners hold toward female counselors; The study will compare the learning styles of individuals from various cultural groups; etc. (the verbs used in the statement of objectives must be specific, measurable, and to a certain extend, observable).

Significance of the Study – Don’t confuse this section with the previous one. Under this section, you are supposed to elaborate on the benefits of your research and indicate to whom the benefits are directed at. For example, an educational research may benefit teachers, parents, school administrators, school counselors, and students. Explain how (exactly) each of these persons would benefit from the findings and results of your study. In other words, you get to defend your research (why is it essential or crucial?). Why will the world be a less better place if your research was not carried out? In other words, you justify the execution of your research under this section. To be convincing, you must write from your heart. Remember, effective persuasion is a matter of the heart as well as the mind. So, it is essential that you sound personal in this section. This is the main thrust of this section.

Statement of Hypotheses or Questions Guiding the Study – Hypotheses are meant for a quantitative study, while Questions are meant for a qualitative study. Hypotheses can be stated in null, or directional, or non-directional forms. Questions must be stated as questions (not as statements that may sound like questions!). Remember, questions here are not similar to your interview or survey questions. These are questions that will guide your study until its completion. So, they must be broad questions that would explore different aspects of the problem under investigation. Do not formulate too many or too few hypotheses or questions. This section of your proposal must correspond to whatever you write under the ‘statement of the problem’ and ‘objectives of the study’ sections. These three sections are closely related.

Basic Assumptions – Assumptions are beliefs or feelings that something is true or that something will happen, although you have no direct way of proving that it is/will. In this section, you have to elucidate the assumptions that you hold while conducting the study. One common assumption that every researcher states in his/her research paper is that he/she assumes that the participants of the study responded to the questionnaire administered to them honestly. Here, ‘honesty’ is something we assume to be present. However, we do not have a way of proving if the participants were indeed honest or otherwise. Writing this section may take a while and requires a lot of thinking. But it is important to present your assumptions so that readers will understand the context of the research and will not use the findings and results of the study carelessly.

Limitations – Every research has its own limitations. Some researches have more limitations than others. It is the duty of the researcher to list down the limitations (of his/her study) to prevent later misuse of research findings and results. Limitations are factors, beyond the control and intent of the researcher, that negatively affect the study. Examples of limitations of a study can be: researcher bias (esp. in a qualitative research), inappropriateness of the interpretive methods utilized, and insufficiency in the selection of sample (small sample size), time constraint, financial constraint, etc.

Delimitations – These are boundaries or scope of the research. In this section, you will talk about generalizability of your study (to what extent can your research findings and results be applied to other similar settings?). You can also write about the scope of the contributions (usefulness) of your research. By doing so, you are actually guarding yourself from being misquoted (unethically) by other researchers or readers in the future.

Definition of Terms – Defining key concepts or terms – clarifying terms that carry specific meaning for the purpose of research – This is where you operationalize your constructs, making them measurable variables (for example, ‘motivation’ is a construct until you define it in measurable terms…so, in your research, you might refer to ‘extrinsic motivation’ as measured by a particular standardized tool when you talk about ‘motivation’). Other terms that need clarification must be defined too. The purpose of defining is to let others know that certain terms mean something very specific in your research. This helps narrow down the breadth of your research.

CHAPTER 2

REVIEW OF RELATED LITERATURE
A summary of the writings of recognized authorities and of previous research provides evidence that the researcher is familiar with what is already known and what is still unknown and untested. Since effective research is based upon past knowledge, this step helps to eliminate the duplication of what has been done and provides useful hypotheses/questions and helpful suggestions for significant investigation. Citing studies that show substantial agreement and those that seem to present conflicting conclusions helps to sharpen and define understanding of existing knowledge in the problem area, provides a background for the research project, and makes the reader aware of the status of the issue. Parading a long list of annoted studies relating to the problem is ineffective and inappropriate. Only those studies that are plainly relevant, competently executed, and clearly reported should be included under this section (be selective; include supporting and contradictory literature related to your topic; incorporate new and old literature) – always end this section with a short summary (your reflection).

CHAPTER 3

METHODOLOGY AND PROCEDURES
This part of the research proposal usually consists of two parts: Type of Research and Research Design

Type of Research – State and explain the type of research you are currently carrying out. Research is broadly categorized as quantitative or qualitative. However, mentioning whether a research is quantitative or qualitative is not sufficient. It is also important that the researcher specifies the specific type of research method that will be utilized to investigate the topic of his/her interest. Examples of methods you might use for a psychological research are: causal-comparative, correlational, survey, descriptive study, experimental or quasi-experimental, historical, ethnography, action research, etc. You might even want to mention why you are choosing to stick to a particular type of research (why is this more appropriate than other types of research?). Brief explanation of the type of research is also essential (in your own words).

Research Design – This is said to be the blueprint or foundation of the whole research project. It gives information about the manner in which the study will be conducted in order to successfully collect and analyze the necessary data. Research Design consists of the following sub-sections:

Subjects (Participants of the Study) – important things to note here: age, gender, grade level, socioeconomic status, race, IQ, mental age, academic achievement level, and other demographics (depending on the nature of the study). The researcher must indicate why a particular population was selected, and justify his/her choice with sufficient proposition in relation to his/her investigation. In a qualitative study, the researcher writes about The Participants of the Study. However, in a quantitative study, the researcher elaborates this section in terms of two other sub-sections called:

Population (how big? why use this population? what are the characteristics of the population?)

Sample (how big? what sampling technique is to obtain the sample group? why this particular size and group? what are the characteristics of the sample?)

Instrumentation – Describe the tools that will be used for the purpose of data collection. Also, defend why you choose to use a particular type of tool or tools and not others. Examples of data collection tools are as follows: Questionnaires, psychological inventories and scales (self-constructed or standardized), observation, interview, etc.

Procedures for Data Collection – This section describes in detail what will be done, how it will be done, what data will be needed, and how the researcher will go about obtaining what is needed. It lists down all the procedures (step-by-step) involved in the process of data collection, from securing permission to enter into research site, until the data is finally collated.

Data Analysis – Under this section, the researcher will write about his/her plan of action to treat the ‘raw’ data collated from research site. In a quantitative study, statistical testing makes up the major part of data analysis. Meanwhile, in a qualitative study, content analysis, meta-analysis, theme-building, pattern-finding, etc. kind of techniques are used to analyze the field notes collated over a period of time.

Time Schedule – This is an important section to write because it will help the researcher to budget his/her time and energy effectively. Dividing the project into manageable parts and assigning dates for their completion helps to systematize the study and minimize the natural tendency to procrastinate.

Copyright June 2006 by Dr. Edward Roy Krishnan, www.affectiveteaching.com[/vc_column_text][/vc_column][/vc_row]