1.2.A—Identify observational units, variables, parameters, and statistics from a statistical study or data set

Identify observational units, variables, parameters, and statistics from a statistical study or data set.

• An observational unit is an item or individual from which a datum is collected.
• A variable is a characteristic that may change from one observational unit to another.
• Data collected on numerical and categorical variables measured on observational units, including photographs, sounds, videos, and text, can convey meaningful information.
• A parameter is a numerical attribute or summary of the variable of interest for a population.
• A statistic is a numerical attribute or summary of the variable of interest for a sample. The value of a statistic from a certain sample is often not equal to the unknown value of the population parameter but may provide the basis for making inferences about the population parameter.