
Population or target population: A population consists of all elements individuals, items, or objects whose characteristics are being studied. The population that is being studied is also called target population. Sample: A portion of the population selected for study. Survey: The collection of information from the elements of a population or a sample. Variable: A characteristic under study that assumes differents values for different elements.
Examples of variables are the incomes of households, the number of houses built in a city per month during the past year, the makes of cars owned by people,...
A variable may be classified as quantitative or qualitative: Qualitative or nonnumeric: Data are called qualitative or nonnumeric if they can not be written down as numbers.
The status of an undergraduate college student is a qualitative variable because a student can fall into any one of four categories: freshman, sophomore, junior, or senior.
Quantitative or numeric: Data are called quantitative or numeric if they can be written down as numbers Quantitative measurements divide further into two types:
