Second, the researcher's intense exposure to study of a case can bias the findings (the case study as a research method); at the least, there are significant opportunities for subjectivity in the implementation, presentation, and evaluation of case study research (Case studies). This high degree of subjectivity opens the door for ethical issues, particularly if the study is being sponsored by a special interest. Third, case studies involve too much investment of time and money to be appropriate for large-scale research projects (Case studies).
Beyea and Nicoll (1997) discuss the many factors that researchers need to consider when selecting a sample for a research project. A researcher must first determine the population of interest (every person, event, or object that meets specific characteristics). If the population of interest has too many members to study, the researcher then needs to formulate a sampling strategy to obtain a subset of the population of interest. The main objective in developing a sampling strategy is to obtain unbiased samples that are representative of entire populations of interest.
Selection of a sampling method depends on the type of study design. Random sampling designs most often are used in quantitative and experimental research designs to ensure that each member or element in the populations of interest has an equal chance of being included in the study sample and to eliminate biases that may occur when selecting samples. If a population of interest cannot be defined clearly, a researcher can select a random sample using sampling designs such as random sampling, stratified random sampling, cluster sampling, and systematic sampling.
Researchers may also choose to use nonprobability sampling methods in which each member or element of a specific population does not have an equal chance of being selected to participate. However, sampling bias limits the generalizability of the study results beyond the study sample. Examples include convenience sampling to save time and money, quota sampling to ensure that certain characteristics are included in study samples, and judgmental sampling to select subjects based on the study's purpose.
The researcher will also need to calculate the sample size. This is based on power, the probability of rejecting the null hypothesis, significance level, and effect size. Researchers must establish thresholds for each of these concepts and then calculate sample sizes using statistical formulas.
When preparing for data collection and analysis for the research project, a researcher should address the following tasks (Data Collection: Procedures, schedule and monitoring):
1) Determine when, where, and how often to collect the data.
2) Develop a schedule for data collection decisions made in Step 1. In addition, decide who will be responsible for each component of data collection.
3) Consider using computer-based project management systems to help coordinate the data collection efforts.
4) Periodically monitor all aspects of data collection to ensure the timely completion of all tasks.
5) Determine what permissions and clearances you will need for gathering your data, then go about seeking them from the appropriate people.
6) to maximize the likelihood that respondents will cooperate, identify what you can do to minimize the burden you place on them.
7) Identify potential risks to the accuracy of the data you will collect. To minimize these risks, decide if it is necessary to implement and carry out procedures to enhance the trustworthiness of the data, such as training programs for data collectors.
8) Administer the procedures identified in Step 6.
9) Screen the data before carrying out analysis to eliminate errors.
Beyea, S.C. And Nicoll, L.H. (1997, October).Selecting samples for research studies requires knowledge of the populations of interest. AORN Journal. http://findarticles.com/p/articles/mi_m0FSL/is_n4_v66/ai_19996778/pg_2/?tag=content;col1
Case studies. http://writing.colostate.edu/guides/research/casestudy/com4a1.cfm
Case study in psychology. http://en.wikipedia.org/wiki/Case_study_in_psychology
Case study: Strengths and weaknesses. http://writing.colostate.edu/guides/research/casestudy/pop4a.cfm
Christensen, L.B. (1994). Experimental methodology ( 6th ed)., Simon & Schuster: Needham Heights, MA.
Data Collection: Procedures, schedule and monitoring. http://oerl.sri.com/module/mod8/m8_p2.html
Difficulties of achieving reliability. http://writing.colostate.edu/guides/research/relval/com2c1.cfm