A sample is a subset or subgroup of the population. It comprises some members selected from it. Only some and not all elements of the population would form the sample. If 200 members are drawn from a population of 500 workers, these 200 members form the sample for the study. From the study of 200 members, the researcher would draw conclusions about the entire population. The Process of picking up the sample is called sampling.
Researcher uses sampling for several reasons. They are explained below;
The cost of conducting a study based on sample is much lesser than the cost of conducting the census study.
Greater accuracy of results:
It is generally argued that the quality of a study is often better with sampling data than with a census. Research findings also substantiate this opinion.
Greater speed of data collection:
Speed of execution of data collection is higher with the sample. It also reduces the time between the recognition of a need for information and the availability of that information.
Availability of population element:
Some situations require sampling. When the breaking strength of materials is to be tested, it has to be destroyed. A census method cannot be resorted as would mean complete destruction of all materials. Sampling is the only process possible if the population is infinite.
The researcher desires to obtain information about a population through questionnaire or testing, he/she has two basic options. Every single member of the population can be questioned or tested. A sample can be conducted that is only selected members of the population are questioned or tested. A difficult questionnaire can be administered to a sample more easily than a brief questionnaire can be administered to the entire population. Not all samples are accurate or appropriate one for gathering information or testing a hypothesis about a population.
Steps in Developing a Sampling plan
A number of concepts, procedures and decisions must be considered by a researcher in order to successfully gather raw data from a relatively small group of people which in turn can be used to generalize or make predications about all the elements in a larger target population. The following are the logical steps involved in the sample execution.
Create an Operating plan for selecting sampling units
Identify the Sampling Frame needed
Select the Data Collection Method
Determine necessary sample size and overall contact rates
Select the Appropriate Sampling Method
Execute the operational plan
Define the target population
2. What factors must you consider when deciding on an appropriate random sampling method?
Determining an appropriate sampling design is a challenging issue and has greater implications on the application of the research findings. The following are the factors to be considered on choosing u on random sampling techniques.
1. Research objectives
A clear understanding of the statement of the problem and the objectives will provide the initial guidelines for determining the appropriate sampling design. If the research objectives include the need to generalize the findings of the research study, then a probability sampling method should be opted rather than a non probability sampling method. In addition the type of research viz., exploratory or descriptive will also influence the type of the sampling design.
2. Scope of the research
The scope of the research project is local, regional, national or international has an implication on the choice of the sampling method. The geographical proximity of the defined target population elements will influence not only the researcher’s ability to compile needed list of sampling units, but also the selection design. When the target population is equally distributed geographically a cluster sampling method may become more attractive than other available methods. If the geographical area to be covered is more extensive then complex sampling method should be adopted to ensure proper representation of the target population.
3. Availability of resources
The researchers command over the financial and human resources should be considered in deciding the sampling method. If the financial and human resource availability are limited, some of the more time-consuming, complex probability sampling methods cannot be selected for the study.
4. Time frame
The researcher who has to meet a short deadline will be more likely to select a simple, less time consuming sampling method rather than a more complex and accurate method.
5. Advanced knowledge of the target population
If the complete lists of the entire population elements are not available to the researcher, the possibility of the probability sampling method is ruled out. It may dictate that a preliminary study be conducted to generate information to build a sampling frame for the study. The researcher must gain a strong understanding of the key descriptor factors that make up the true members of any target population.
6. Degree of accuracy
The degree of accuracy required or the level of tolerance for error may vary from one study to another. If the researcher wants to make predictions or inferences about the ‘true’ position of all members of the defined target population, then some type of probability sampling method should be selected. If the researcher aims to solely identify and obtain preliminary insights into the defined target population, non probability methods might prove to be more appropriate.
6. Perceived statistical analysis needs
The need for statistical projections or estimates based on the sample results is to be considered. Only probability sampling techniques allow the researcher to adequately use statistical analysis for estimates beyond the sample respondents. Though the statistical method can be applied on the non probability samples of people and objects, the researcher’s ability to accurately generalize the results and findings to the larger defined target population is technically inappropriate and questionable. The researcher should also decide on the appropriateness of sample size as it has a direct impact on the data quality, statistical precision and generalizability of findings.
3. What are the main differences among structured interviews, semi structured interviews and unstructured interviews ?
The structured interviews are conducted when the interviewer knows the type of questions to be asked to the respondents or when the information needs are clearly known. The questions may focus on the issues that have been highlighted during the unstructured interviews and are considered relevant to the problem identified. The interview may be conducted by the researcher himself or by a team of interviewers. The researcher/ interviewer should be very clear about the purpose of each question particularly when a team of interviewers conduct the survey. The same questions are posed in the same sequence or manner to all the respondents and the responses are noted down. Depending on the situations and the respondents willingness and knowledge the researcher can also ask other relevant questions which may not be in the list so as to gain more insight into the identified problem. The researcher may also include visual aids, drawings , pictures and other materials in conducting the interviews. In situations where the ideas cannot be clearly articulated only with words visual aids are more useful.
Structured interviews require set of rules. Each question should be read word by word by the researcher without any deviation. Structured interviews are the type used most often by quantitative researchers. Example: bodily posture, facial expressions and emotional affect.
Semi structured interviews
Semi structured interview are more relaxed than structured interviews. Researchers use this type to cover every question in the protocol, they have some to explore participant responses by asking for clarification or additional information. Interviewers also have the freedom to be more friendly and sociable. Semi-structured interviews are most often used in qualitative studies. Data sets obtained using this style will larger than those with structured interviews.
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In the unstructured interviews, the interviewer does not conduct the interview with a planned sequence of questions. The aim of this interview is to highlight the preliminary issues so that the researcher can determine the variables which needs further in-depth investigation. The researcher resorts to the unstructured interviews when the problem is not clearly formulated or when a clear understanding of the variables involved is not present. The researcher in the attempt to obtain information may adopt different styles and sequencing of questions to various respondents. Some may provide information with open ended questions, whereas some may require more directions. Some respondents may be more defensive and may not to willing to share information. Some may be even reluctant to undergo the interview and may refuse to respond. The researchers have to employ various questioning techniques so as bring the respondents defenses down and make them more amenable to reveal information. The researcher should also know when to retreat or terminate the interview when the respondents cannot be convinced to participate or impart the information.
The unstructured interview will direct the researcher to understand the variables which need greater focus based on which a structured interview can be planned. Unstructured interviews in this type, researchers need only topics to be covered during the interview. There is no order and no script. The interaction between the participant and the researcher is more like a conversation than an interview. Unstructured interviews are often used in case studies (types of qualitative studies).
4. Consider the following different types of data and state if you consider them amenable to quantitative or qualitative analysis or both:
i) A collection of scripts taken from semi structured interviews with 150 prisoners asking them about their attitudes to the regime of discipline in the prison.
ii) The results of a questionnaire sent to all UK solicitors practices, asking about their fee income, insurance premiums, turnover and staffing levels.
iii) A survey of government statistics about SME business failures in the last 20 years.
Quantitative and Qualitative Approaches
Most of the research is of the quantitative type. In such research, we rely on measuring variables and comparing groups on those variables, or examining the strength of the relationship between two or more variables. The belief here is that objectivity in the data collection process is paramount. Whoever was repeating this study or using the same instruments and methods would get approximately the same numbers.
Quantitative research relates to aspects that can be quantified or can be expressed in terms of quantity. It involves the measurement of quantity or amount. The various available statistical and econometric methods are adopted for analysis in such research.
Another approach available is qualitative approaches. These approaches employ more subjective approaches and frequently use interviews, focus groups, or single case designs, that lack objective measurement or have restricted generalisability. However, these methods are becoming more widely used these days as analysis methods improve and people search for better ways of gathering data about a problem. This can be a quite subjective, laborious, and costly process, but with a standardized set of guidelines, specific training, and greater familiarity with the technique, the considerable richness of these methods has been able to be tapped.
Qualitative research is particularly helpful in identifying the scope of the research that should be pursued to fully understand the views, opinions and attitudes that may be encountered. It also allows to probe in depth how consumers reach a decision in the buying process. Qualitative research can even lead to formulating the hypotheses that will be tested through quantitative research. Qualitative research is particularly significant in the context of behavioral science, which aim at discovering the underlying motives of human behavior.
Qualitative research differs from quantitative research in the following ways:
The data is usually gathered using less structured research instruments
The findings are more in-depth since they make greater use of open-ended questions
The results provide much more detail on behavior, attitudes and motivation
The research is more intensive and more flexible, allowing the researcher to probe since he/she has greater latitude to do so
The results are based on smaller sample sizes and are often not representative of the population,
The research can usually not be replicated or repeated, giving it low reliability; and
The analysis of the results is much more subjective.
The large number of scripts suggests that some of the quantitative analysis are possible and assume that there are some standardization is possible whereas qualitative analysis is used for wider range of opinion.
Based on these theories the above questions can answered as follows.
i) Research is critically an important thing in providing knowledge need for informing and enlighten prison policy, as well as for affording health benefits to prisoners. At the same time, research could impose unacceptable risks on prisoners, complicated by serious concerns about the potential for coercion in the prison environment. For this a qualitative analysis should be used.
ii) The report of Solicitors market provides an a complete analysis about income, turnover and the like, all are quantitative data. It discusses the relative performance of the main professions and assesses the profitability and claims experience of the whole market. The research also includes an in-depth analysis of the distribution and competitive landscape and forecasts the market size. Insight into the different channels and platforms of distributing professional indemnity insurance products. Analysis of the total premiums and market share for the largest professional indemnity insurance groups. For this type quantitative analysis should be used.
iii) A survey of Government statistics about SME business failure I last 20 years involves both of qualitative and quantitative data. So this analysis both Qualitative and Quantitative type of analysis should be used.