A promise is a declaration given by someone of something that will be done in the future

A promise is a declaration given by someone of something that will be done in the future. Sampling theory
The sampling theory describes the methods of random selection of a population in a research, data collection from the population and the analysis of the collected data so as to prove hypotheses. Sampling theory is a research design often used by scientists where estimation methods and a random selection of the population is applied (Sampling Theory, 2018).
Stratified Sampling
This type of study involves collecting samples from different portions of the population called strata which are assumed to be independent and that they do not overlap with each other. The different portions should cover the entire populations so as to get reliable output (Banning, Camstra, & Knottnerus).
Cluster sampling
The target population in cluster sampling is initially divided into groups called clusters. The elements of each cluster are critically analyzed and a sample population is randomly selected from each group. These will represent the entire population during the research. The clusters should be independent and should not overlap with each other (Banning, Camstra, & Knottnerus).
Simple random sampling without replacement
This sampling theory involves picking a subject from a densely populated group and no other subject is put in its place. The selection is random; therefore, any member of the population could be selected. The sample is collected from the entire population rather than splitting it into groups (Banning, Camstra, & Knottnerus).
Discuss generalizability as it applies to nursing research
Generalizability is a mode of research, usually conducted in fields of study where there is active improvements or evidence of the same. It is often used in quantitative research where general conclusions are drawn from the target population based on the already observed characteristics. Nursing is an actively growing field which calls for improvements periodically, hence, the need for generalization. Generalization aids in identifying and improving flaws in the nursing field and using the results from a research on a sample group to determine that of a larger one (Polit & Beck, 2010).