| What is a cluster sample? | a probability sample that is used when no list of elements exists. The sampling frame initially consists of clusters of elements |
| What is confidence (in a statistic)? | the degree of belief that an estimated range of values - more specifically, a high or low value - includes or covers the population parameter |
| What is a convenience sample? | a nonprobability sample in which the selection of the elements is determined by the researcher's convenience |
| What is a disproportionate sample? | a stratified sample in which elements sharing a characteristic are underrepresented or overrepresented in the sample |
| What is an element? | a particular case or entity about which information is collected; the unit of analysis |
| What is an estimator? | a statistic based on sample observations that is used to estimate the numerical value of an unknown population parameter |
| What is an expected value? | the mean or average value of a sample statistic based on repeated samples from a population |
| What is a nonprobability sample? | a sample for which each element in the total population has an unknown probability of being selected |
| What is non-response bias? | Non-response bias occurs when some sampled subjects cannot be reached or refuse to participate or fail to answer some questions. |
| What is a probability sample? | a sample for which each element in the total population has a known probability of being selected |
| What is a proportionate sample? | a probability sample that draws elements from a stratified population at a rate proportional to the size of the samples |
| What is a purposive sample? | a nonprobability sample in which a researcher uses discretion in selecting elements for observation |
| What is a quota sample? | a nonprobability sample in which elements are sampled in proportion to their representation in the population |
| What is random digit dialing? | a procedure used to improve the representativeness of telephone samples by giving both listed and unlisted numbers a chance of selection |
| What is a random start? | selection of a number at random to determine where to start selecting elements in a systematic sample |
| What is sample bias? | the bias that occurs whenever some elements of a population are systematically excluded from a sample. It is usually due to an in complete sampling frame or a nonprobability method of selecting elements |
| What is a sampling distribution? | a theoretical (nonobserved) distribution of sample statistics calculated on samples of size N that, if known, permits the calculation of confidence intervals and the test of statistical hypothesis |
| What is sampling error? | the difference between a sample estimate and a corresponding population parameter that arises because only a portion of a population is observed |
| What is a sampling fraction? | the proportion of the population included in the sample |
| What is a sampling interval? | the number of elements in a sampling frame divided by the desired sample size |
| What is a sampling unit? | the entity listed in a sampling frame. It may be the same as an element, or it may be a group or cluster of elements |
| What is a simple random sample? | a sample in which each element has an equal chance of being selected |
| What is a snowball sample? | a sample in which respondents are asked to identify additional members of a population |
| What is statistical inference? | the mathematical theory and techniques for making conjectures about the unknown characteristics (parameters) of populations based on samples |
| What is a stratified sample? | a probability sample in which elements sharing one or more characteristics are grouped, and elements are selected from each group in proportion to the group's representation in the total population |
| What is a stratum? | a subgroup fo a population that shares one or more characteristics |
| What is a systematic sample? | a probability sample in which elements are selected from a list at predetermined intervals |
| What is a weighting factor? | a mathematical factor used to make a disproportionate sample representative |