General rule - as large as possible to increase the representativeness of the sample Increased size decreases sampling error Relatively small samples in qualitative, exploratory, case studies, experimental and quasi-experimental studies Descriptive studies need large samples; e. Type I and Type II errors Type I error Based on the statistical analysis of data, the researcher wrongly rejects a true null hypothesis; and therefore, accepts a false alternative hypothesis Probability of committing a type I error is controlled by the researcher with the level of significance, alpha.
This glossary contains terms used when planning and designing samples, for surveys and other quantitative research methods. Abduction A useful but little-known concept first used by the philosopher Peirce around Similar to inductionit has been described as "testing a theory by fitting it over a framework of facts.
Adaptive sampling A method used for sampling rare populations. When you find something that you're interested in, you start to look more closely at nearby areas.
For example, if you're studying a rare disease and find somebody who has it, you sample their neighbours as well. This is often used in quality control - e. Adaptive sampling is more efficient than random sampling, but calculating population estimates becomes more complex.
Analysis Understanding something by dividing into smaller parts, and studying each part separately. The opposite of analysis is synthesis.
Survey analysis involves considering the responses to each survey question and pairs of questions. Axiom A statement that is so obvious that it's a starting point for any research.
For example, the laws of arithmetic are axioms. To say that something is axiomatic is to imply that it must be true.
Sometimes axioms are revealed to be assumptions that are not always true. Birthday rule When a researcher contacts a household and says "I'd like to interview the person who last had a birthday" this is not an advertising gimmick, but a way of ensuring randomness - it assumes that people's birthdays are spread evenly across the year.
Census Survey of a whole population. Most countries have a Population Census with a capital C every 5 or 10 years, but a researched population can be much smaller. Thus a census with a small c of all staff of an organization would be a survey where everybody was sampled.
Their parents' permission is needed to interview them. Some countries have specific laws on this, and have higher age limits - up to Cluster When you are surveying people in their homes, it's very expensive to travel all around a city, interviewing at one home in each suburb.
For efficiency, most door-to-door surveys use cluster sampling, where a starting address is chosen at random, and interviewing is done at a number of nearby homes - often about 10 of them. Convenience sample Using a sample of people who happen to be handy or easy to survey.
May be OK in preliminary research, but not guaranteed to be representative of the population. Deduction Deduction is what you do when you know the principles of something, and deduce a particular case.
Induction is the opposite process.
Dependent variable A statistical term for whatever measure you are trying to predict. See independent variable and regression. Dwelling The premises where a household lives. May be a house, flat, caravan, boat, etc. It is a place, not a group of people.
Effective sample size If you interview two people at the same household, and ask them a question they give the same answer to - such as "how many TV sets are in your home? People in the same household tend to give identical answers, so in order not to waste interviews, it's often best to interview only one person per household.
Empirical Based on actual data. The opposite of empirical is theoretical. Error types Because a survey doesn't include all members of a population, or include all possible questions, various types of error can occur Type I error error of the first kind:As part of CASRO's great series of webinars, John Bremer of The NPD Group discussed "Elements of Non-Probability Seminar."Besides touching on probability sampling, sample matching, and calibration, he presented an excellent taxonomy of the different types of non-probability sampling.
Edexcel BTEC Level 3 Nationals specification in Business 1 – Issue 2 – June © Edexcel Limited Unit Market Research in Business. Probability sampling.
In probability sampling, each member of a given research population has an equal chance of being initiativeblog.com involves, literally, the selection of respondents at random from the sampling frame, having decided on the sample size.
Populations: Definition - a complete set of elements (persons or objects) that possess some common characteristic defined by the sampling criteria established by the researcher Composed of two groups - target population & accessible population Target population (universe) The entire group of people or objects to which the researcher wishes to generalize the study findings.
In statistics, quality assurance, and survey methodology, sampling is the selection of a subset (a statistical sample) of individuals from within a statistical population to estimate characteristics of the whole population.
Statisticians attempt for the samples to represent the population in question. Two advantages of sampling are lower cost and faster data collection than measuring the.
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