Population The whole set of items that are of interest in statistics.

Census An observation or measurement of every member of a population.

Sample A selection of observations taken from a subset of the population.

Sampling Units Individual units of a population.

Sampling Frame A list formed by naming or numbering the sampling units of a population.

Simple Random Sample A sample where every sample of size n has an equal chance of being selected.

Systematic Sampling A method where required elements are chosen at regular intervals from an ordered list.

Stratified Sampling A sampling method where the population is divided into mutually exclusive strata and a random sample is taken from each.

Quota Sampling A sampling method where an interviewer selects a sample that reflects the characteristics of the whole population.

Opportunity Sampling A method of sampling where participants are selected based on their availability and fit for the study criteria.

Quantitative Variables Variables associated with numerical observations.

Qualitative Variables Variables associated with non-numerical observations.

Continuous Variable A variable that can take any value within a given range.

Discrete Variable A variable that can take only specific values within a given range.

Grouped Frequency Table A table that presents data in groups or classes without showing specific data values.

Class Boundaries The maximum and minimum values that belong in each class of a grouped frequency table.

Midpoint The average of the class boundaries in a grouped frequency table.

Class Width The difference between the upper and lower class boundaries.