Definitions

- Statistics
- Collection of methods for planning experiments, obtaining data, and then organizing, summarizing, presenting, analyzing, interpreting, and drawing conclusions.
- Variable
- Characteristic or attribute that can assume different values
- Random Variable
- A variable whose values are determined by chance.
- Population
- All subjects possessing a common characteristic that is being studied.
- Census
- The collection of data from
*every*element in a population. - Sample
- A subgroup or subset of the population.
- Parameter
- Characteristic or measure obtained from a population.
- Statistic (not to be confused with Statistics)
- Characteristic or measure obtained from a sample.
- Descriptive Statistics
- Collection, organization, summarization, and presentation of data.
- Inferential Statistics
- Generalizing from samples to populations using probabilities. Performing hypothesis testing, determining relationships between variables, and making predictions.
- Qualitative Variables (Data)
- Variables (data) which assume non-numerical values.
- Quantitative Variables (Data)
- Variables (data) which assume numerical values.
- Discrete Variables (Data)
- Variables (data) which assume a finite or countable number of possible values. Usually obtained by counting.
- Continuous Variables (Data)
- Variables (data) which assume an infinite number of possible values. Usually obtained by measurement.
- Nominal Level
- Level of measurement which classifies data into mutually exclusive, all inclusive categories in which no order or ranking can be imposed on the data.
- Ordinal Level
- Level of measurement which classifies data into categories that can be ranked. Differences between the ranks do not exist.
- Interval Level
- Level of measurement which classifies data that can be ranked and differences are meaningful. However, there is no meaningful zero, so ratios are meaningless.
- Ratio Level
- Level of measurement which classifies data that can be ranked, differences are meaningful, and there is a true zero. True ratios exist between the different units of measure.
- Random Sampling
- Sampling in which the data is collected using chance methods or random numbers.
- Systematic Sampling
- Sampling in which data is obtained by selecting every
*k*th object. - Convenience Sampling
- Sampling in which data that is readily available is used.
- Stratified Sampling
- Sampling in which the population is divided into groups (called strata) according to some characteristic. Each of these strata is then sampled using one of the other sampling techniques.
- Cluster Sampling
- Sampling in which the population is divided into groups (usually geographically). Some of these groups are randomly selected, and then all of the elements in those groups are selected.
- Self-Selected Survey
- Sampling in which the respondents themselves decide whether or not to be included.
- Observational Study
- A study in which the subjects are observed and studied, but no attempt is made to manipulate or modify the subjects.
- Experiment
- A study in which a treatment is applied, and then its effects on the subjects are studied.
- Sampling Error
- The difference between the sample result and the true population result that occurs because of chance variation.
- Non-sampling Error
- An error that occurs because sample data is incorrectly collected, recorded, or analyzed.

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James Jones