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Nursing Resources: Sampling Methods and Statistics

Sampling Methods

Probability sampling (random sampling)

ο  It is a selection process that ensures each participant the same probability of being selected.
ο  Random sampling is the best method for ensuring that a sample is representative of the larger population.
ο  Random sampling can be:

  • simple random sampling
  • stratified random sampling, and
  • cluster sampling.

Nonprobability sampling

ο  It is the selection process in which the probability that any one individual or subject selected is not equal to the probability that another individual or subject may be chosen.
ο  The probability of inclusion and the degree to which the sample represents the population are unknown.
ο  The major problem with nonprobability sampling is that sampling bias can occur.
ο  Nonprobability sampling can be:

  • convenience sampling
  • purposive sampling or
  • quota sampling

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Instruments in Nursing Research

  • An instrument in a research study is a device used to measure the concept of interest in a research project.
  • It is used to measure a concept of interest.
  • An ideal measuring instrument is one which results in measures that are relevant, accurate, objective, sensitive and efficient.
  • Measures which are Physical and physiological have higher chance of success in attaining these goals than measures that are psychological and behavioral.
  • Instruments can be:
    • observation scales,
    • questionnaires or
    • interview schedules.
  • Validity and reliability are two statistical properties used to evaluate the quality of research instruments (Anastasi, 1986).
  • It is important that assessment techniques possess both validity and reliability.

Sampling Methods

Suresh KP and Chandrashekara, S. Sample size estimation and power analysis for clinical research studies.Journal of Human Reprouductive Sciences. 2012 Jan;5(1):7-13. doi: 10.4103/0974-1208.97779.

Difference Between "Population" and "Sample"

While "population" is about the generality of the universe or groups of people, "sample" refers to a fraction of persons from the population.

It is from the sample that data is collected in the course of a study, and because that sample is representative of the population, the results can be generalized to the population in a scientific study.