When determining the size of sample, researchers should know the number of animals or people needed since having inadequate sample size influence the overall results of the study (National Cancer Institute, 2012). Statistical power (p) level, error, and treatment variability are parameters which help researchers in choosing the appropriate sample size for a research (National Cancer Institute, 2012). Statistical power reveals how strongly participants will be influenced by treatment provided to them. The level of (P) assists researchers to determine probability of any variations within the subjects during the research (National Cancer Institute, 2012). Lastly, researchers determine the appropriate sample size depending on whether the study treatment variability is above the error variability or not. Denoting, more study participants may be required if the investigator determines that the influence of the treatment is below the error variability (National Cancer Institute, 2012).
The selected sample size calculators are Raosoft and Creative Research Systems. The calculators have a field for the entry of confidence interval, which then establishes the margin of error which will arise depending on the study participants’ responses (Creative Research Systems, 2010; Raosoft.com, 2004). In addition, the calculators provide the choice to choose confidence level, which represents proportion of how confident investigators are that study participants will accept the results estimated by researchers (Creative Research Systems, 2010; Raosoft.com, 2004). The systems propose the size of the sample depending on the confidence interval, the chosen confidence level, and population entered. Using a population of 100, 000, 3% confidence interval and 95% confidence level to test the calculators. Based on a no or yes type of research, the result of both calculators give a 95% of the time, amid 47 percent and 53 percent of the participants gives a yes on every survey question (Creative Research Systems, 2010; Raosoft.com, 2004). The test, moreover, determine that a sample size of 1056 is needed to represent 100, 000 population (Creative Research Systems, 2010; Raosoft.com, 2004).
Creative Research Systems. (2010). Sample Size Calculator. Retrieved November 20, 2013, from http://www.surveysystem.com/sscalc.htm#one
National Cancer Institute. (2012). Determination of Sample Size. Retrieved November 20, 2013, from http://web.ncifcrf.gov/rtp/lasp/intra/acuc/fred/Determination_of_Sample.pdf
Raosoft.com. (2004). Sample Size Calculator. Retrieved November 23, 2011, from http://www.raosoft.com/samplesize.html