A population is the set of all individuals with particular characteristics that are of interest to the researcher(s). For instance, female hockey players in a nation can be a population. On the other hand, a sample is the subset of the population that represents it in the research (Latham, 2007). A sampling frame consist of all possible sampling units (the individual, sport, area, or institution from whom or which the researcher wishes to collect data). In an ideal state, the sampling frame coincides with the population (Buskirk, 2016). Not all instances follow this trend because there could be peculiar differences that could exclude some part of the population.
A representative sample represents the population characteristics accurately. In random sampling, the researcher randomly selects the elements, and each one of them has an equal chance of appearing in the sample chosen (“sampling,” n.d.). On the contrary, in a systematic sampling, the scientist(s) picks the subjects in a regular pattern by skipping some of them at particular regular intervals (Kulshreshtha, 2013). Both random and systematic sampling are probabilistic. Quota sampling is a non-probability method involving picking the samples from specified subgroups of the population. For instance, picking people based on their ages i.e. 20-30, and 31-40, etc. Purposeful sampling is also a non-probabilistic method that involves judging the subjects based on particular criteria set by the researcher. For example, selecting people with a bald head and a specific medical condition.
According to Yumane (1967) formula, n=N1+N(e)2 whereby n-sample size, N-population, e-is precision level. With a confidence level of 95% and an accuracy level of ±10%, a population five hundred would have a sample population of 83 (Israel, 2015).
References
Buskirk, T., 2016. Target Population and Sampling Frame in Survey Sampling. The Analysis Factor RSS. Available from: http://www.theanalysisfactor.com/target-population- sampling-frame/ [Accessed April 22, 2016].
Israel, G.D., 2015. Determining Sample Size1. EDIS New Publications RSS. Available from: https://edis.ifas.ufl.edu/pd006 [Accessed April 22, 2016].
Kulshreshtha, A. C., 2013. Basic Concepts of Sampling- Brief Review: Sampling Designs. Second RAP Regional Workshop. http://www.unsiap.or.jp/e- learning/el_material/Agri/rap2/ag_02_04_L2.1_SamplingDesigns.pdf [Accessed on April 22, 2016].
Lathan, B. 2007. Sampling: What is it? [Pdf] Available at: <http://webpages.acs.ttu.edu/rlatham/Coursework/5377%28Quant%29%29/Sampling_M ethodology_Paper.pdf> [Accessed April 22, 2016]
Sampling. [Pdf]). Available from: http://www.stat.yale.edu/courses/1997-98/101/sample.htm [Accessed April 22, 2016].
