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Target Population- The target population is a group of individuals who meet a particular set of sampling criteria, such as: female, 18 years or older, new diagnosis of type II diabetes, not on insulin. Accessible population- The portion of the target population to which the researcher has reasonable access. The accessible population might include elements within a country, state, city, hospital, nursing unit, or primary care clinic. Generalizationextends the findings from the sample under study to the larger population. Representativeness of a sample – means that the sample, accessible population and target population are alike in many ways. In quantitative research, you need to evaluate representativeness in terms of the setting, characteristics of the subjects, and the distribution of values on variables measured in the study. Random Variation – the expected difference in values that occurs when different subjects from the same sample are examined; as the sample size increases, random variation decreases, improving the representativeness of the results. Systemic Variation: a consequence of selecting subjects whose measurement values differ in some specific way from those in the general population; bc these subjects have something in common, there may be some bias. *In studies with high acceptance rate & low refusal, high retention rates less chance for Systemic variation & sample is more likely to be representative of the target pop. Probability Sampling: every person of the pop has an opportunity to be selected for the sample. Simple random sampling- Simple random sampling is achieved by randomly selecting elements from the sampling frame. Ex. names on a slip of paper and draw from a basket, using a random numbers table, etc. Stratified random sampling- Stratified random sampling is used in situations in which the researcher knows some of the variables for the population that are critical for achieving representativeness. Cluster sampling- In cluster sampling, a researcher develops a sampling frame that includes a list of all the states, cities, institutions, or organizations in which elements of the identified populations can be linked. A random sample of these can then be used in the study. Systematic samplingused when an ordered list of all members of the population is available. The process involves selectingevery kth individual on the list, using a starting point selected randomly. Non Probability methods:Convenience sampling- Subjects are asked to be in the study because they are "in the right place at the right time". It provides little opportunity to control for biases.Quota sampling- Convenience sampling with a strategy to ensure the inclusion of subject types likely to be underrepresented in the convenience sample, such as females, minority groups, the elderly, etc.