In your response to your classmate provide feedback on the proposed sample size for their research proposal. Do you agree with their reasoning, why or why not?
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Samples that are too small to appropriately represent a population in a study may work to undermine internal and external validity.1 There are statistical and ethical considerations to note when selecting a sample size.1 From the statistical approach, too small a sample size may prevent important findings from being extrapolated.1 The need for the appropriate sample size directly relates to the study’s capability of detecting differences with clinical significance.1Detecting clinically significant differences are often the main goal of a research study.2 The primary influence that a very small sample size has is its effect on statistical power.1 Statistical power is refers to the study’s ability to demonstrate traits that truly exist in the study population.1 Too small a sample size may fail to accurately represent traits that are truly present in the study population.1 A Type II Error or false-negative may occur, which may result in an incorrect acceptance or rejection of a research hypothesis.1 When the sample of the population is to be further subdivided, in a case of too small a sample size, the even smaller groups will likely yield an even more pronounced occurrence of Type II Error or problems with significance.1 From an ethical approach, a very small sample size which fails to meet the study goals could mean research study participants may have to endure risk, suffering or inconvenience in vain.2 Additionally, hard to come by resources of money and time may be wasted on a study that will not provide any significant clinical benefit or improvement in the participant’s quality of life.2
The sample size that appears to work best for my research proposal:
95% confidence level Z=2.2 confidence interval population=1,000 sample size needed= 665
This sample size is large enough to yield a sample mean close to the true population value. This sample size will not be so small that it will likely result in an error or a misrepresentation of the population.
References:
1.) Jacobsen, Kathryn H. (2011). Introduction to Health Research Methods: A Practical Guide, 2nd Edition. Jones & Bartlett Learning, MA.
2.) Faber J, Fonseca LM. How sample size influences research outcomes. 2014;19(4). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4296634/pdf/dpjo-19-04-0027.pdf. Accessed February 6, 2017.
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