Why is it important that a sample be random and representative when conducting hypothesis testing?
To conceptualize the sampling, one can start from the definition that it is the operation of collecting a representative sample for the analysis. It can also be defined as a process in which the collection will be of a representative portion of a heterogeneous batch, that is, that represents the totality of the material of interest for the analysis to be performed.
Sampling may also be characterized as an art, as it often requires the sampler to have creative skills in certain situations to obtain representative sampling. It is a sequence of stages of preparation such as crushing, grinding, drying, homogenization, transfer, among others, and sampling stages proper (reduction of mass of material), both susceptible to change in the content of the characteristic of interest and, to the generation of preparation errors and sampling errors(Minnitt,2014).
The tools to verify if a sample is reliable (representative) are the same ones used for the analytical method, however, the variables can be considered different, for example: while in an analytical method for solids the concern is in the weighing, in the sampling is in the variability of the particle size.
The first step of analysis is to subject the sample to suitable treatment, aiming at its preparation to progress in the steps that form a chemical analysis (Savic & Sample, 2017). Often, sampling is the most difficult step and the source of the biggest errors. The reliability of the results of the analysis will never be greater than the reliability of the sampling step after the entire portion analyzed is only a small percentage of the total product.
Minnitt, D. (2014). Sampling 2014 What does academia get from Sampling and WCSB conference(s)? .TOS Forum, 2014 (3), 21.
Savic, O., & Sample, H. (2017). What makes for conceptual similarity?. Theoria, Beograd, 60(4), 77-90.
by EssayRoyal, Dec. 6, 2019, 6:08 p.m.