Sample Size and Power
Introduction The contemporary research environment ordinarily involves the incorporating of human or animal subjects, who are to be essentially subjected to an identified process/treatment.
Hence, in a bid to establish the relationship between the chosen sample size and resultant effect, it is critical to conduct a case analysis to determine the power. Power is essentially the sensitivity level of the study in detecting a statistically proven difference based on the observed study magnitude (Saeed, Pervaiz, & Shahbaz, 2006). Determining Sample Size Requirements Before beginning the process of determining sample size requirements it is important to identify the type of samples required and whether they are dependent or independent. This will lead to identification of variables like mean, proportion, odds ratio or slope. Moreover, it is also important to establish the degree of relative precision required. This varies depending on the type of research being carried out.
For instance, most of the established methods for calculating sample size to indicate the impending relationship between disease and exposure and disease are based on the relative risk factor (Browner & Newman, 1989). Defining Sample Size Characteristics Sample size characteristics entail a description of the unique elements associated with a sample, which in turn have an effect on produced by the alternate hypotheses in an experiment. This has a potential efect on the resultant power analysis framework. Sample size depends on: population parameters for determining difference between proportion and means; minimization of variance; issues and prior information, clinical trials; power analysis; and cost (Saeed, Pervaiz & Shahbaz, 2006). Importance of Effective Size during Power Analysis The projected or actual size of the samples effectively determine the potential effect, which affects results of power analysis.
This especially depends upon the elements associated with the alternate hypothesis of the research or experiment. Hence, the study needs to be of adequate size matching the chosen study goals (Lenth, 2001). Failure to do proper judgment can lead to potential errors. For instance, if a sample is under-sized this could lead to a potential waste of resources, which affects the production of useful results (Lenth, 2001).Control Elements for Power The control elements of power include the proposed hypotheses (positive and null hypothesis), independent/dependent samples, alpha, and potential effect size.
Moreover, power involves specifying a particular hypothesis test for a parameter, specifying the expected significance level, specifying an effective size reflecting alternate scientific view, obtaining existing/historical values for pre-empting the power function, and specifying the expected target value (Lenth, 2001). Ethical Perspectives Some of the ethical perspecctives arising from the effect of sample size and power analysis usually depend on assessment result of the risk potential and decision framework used to establish the sample size. This leads to the potential occurrence of harm, flaws, and provision of false forms of assurance leading to misinterpretation. Flaws arise due to: assumption the existence of a meaningful boundary between inadequate and adequate sample sizes, reliance on inputs that are incapable of being verified, and failure to suggest modes of using final information (Bacchetti, 2010). Moreover, there various forms of manipulations usually done to attain desired results.
This especially involves the manipulation of final sample size calculations with an aim of producing the desired results, commonly described as ‘sample size game.’ (Bacchetti, 2010). Ethical perspectives also arise on account of projected power assumptions. The risk of using an inadequate projected value, which is not matching the participant burden mostly, applies to studies which are too large of too small to be deciphered (Bacchetti, 2010). ConclusionHence, it is important to identify the fact that there exists a significant relationship between the projected power and sample size of a research experiment. This primarily because the determination of sample size requirements, sample size characteristics, projection of an effective size, control elements of power, and ethical perspectives play a critical role in an effective research study depending in chosen hypotheses (positive and null) and sample parameters.
