In common usage, data are a collection of discrete or continuous values that convey information, describing the quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpreted formally. A datum is an individual value in a collection of data. Data are usually organized into structures such as tables that provide additional context and meaning, and which may themselves be used as data in larger structures. Data may be used as variables in a computational process. Data may represent abstract ideas or concrete measurements. Data are commonly used in scientific research, economics, and in virtually every other form of human organizational activity. Examples of data sets include price indices, unemployment rates, literacy rates, and census data. In this context, data represent the raw facts and figures from which useful information can be extracted.