Nonresponse is a problem in many surveys.think of it as the examplethey gave in the book "I know its dinnertime, but i'm sure yu wouldnt mind answering a few questions, it'll only take about twenty minutes.oh youre busy?" another example inculdes those who are at work durting the day won't respond to a telephone survey only conducted during the workday. Voluntary response is a form of nonresponse bias.but it may occur for many other reasons. those who do respond are likely to not represent the entire group. Nonresponse bias- Bias introduced to a sample when a large fraction of those sampled fail to respond.
Undercoverage- a sampling scheme that does not inclue some part of the population and/or makes them have less representation than it does have in the population. Samples based on voluntary response are always invalid and cannot be recovered, no matter how large the sample size.Ĭonvenience sampling- Simply include the individuals who are at hand. Voluntary response bias- Bias introduced to a sample when individuals can choose on their own whether to participate in the sample. When there is no relationship between the order of the sampling frame and the variables of interest, a systematic sample can be representative. Systematic sampling- a sample drawn by selecting individuals systematically from a sampling frame. Multistage sampling- sampling method that uses and combines several other sampling methods to make more randomization. Used for convenience, practicality, or cost. Stratified random sample- a sampling design where the population is divided into subpopulations (strata) and then random samples are taken from each stratum.Ĭluster sampling- sampling method where an entire group (cluster) is chosen at random. Strata- homogenous groups that are used to split up the population before a sample is chosen. Homogeneous groups- population that is split up into groups that are alike for example (men, women). Sampling variability- the differences between each sample that we draw at random "sample-to-sample differences* Sampling frame - A list of individuals from whom the sample is drawn individuals who may be in the population of interest but who are not in the sampling frame cannot be included in any sample. This is what we measure all other sampling methods against and what we hope every sampling method is achieving. Simple Random Sample (SRS)- each combination of people has an equal chance of being selected. Statistic- any summary found from the data Parameter- The numbers in the model that have to be chosen to explicitly determine the value of the model. The best defense against bias is randomization.Ĭensus-a sample that consists of the entire population. Randomization- Each individual is given a fair, random chance of selection. Sample survey- a study that asks questions of a sample drawn from some population in the hope of learning something about the entire population.īiased- a sample that does not represent the population in some way, it overlooks an important group. Sample- A smaller group of individuals selected from a population. Population- A large group of individuals usually impractical to measure.
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