The terms "standard" and "part number" are frequently used interchangeably, which can lead to some confusion.
Many companies refer to the products they manufacture as "parts" and so they assign "part numbers" to distinguish one product from another, but this practice is not universal. Other companies call their products what they are—chocolate chip cookies, for example—and then assign a characteristic to the name—weight, for this example. So the standard might be "chocolate chip cookies 16 oz." Standards for other products in this fictitious company might be "chocolate chip cookies 4 oz.," chocolate chip cookies 8 oz," and so forth.
A standard represents one characteristic of the part number, item, or process that you are studying.
Even though the standard identifies a characteristic of the item or process, a part number (or product name) along with a characteristic are commonly referred to as a "standard."
The simple answer is as many characteristics for a product that you want to measure.
If three characteristics—length, protrusion length, and out-of-round for example—are measured on part number D-34KW, then three plausible standards for this part might be:
D-34KW LENGTH,
D-34KW PROTRUSION LENGTH, and
D-34KW OUT-OF-ROUND
To generate charts and reports, it is necessary to create a standard for each characteristic of a part before data can be entered to generate charts and reports on those characteristics.
This stores the main information you need for the part number and characteristic—including the subgroup size, the upper- and lower-specification limits, and the number of decimal places to display.
A process specification is very similar to a standard, but it represents the combination of process and characteristic instead of part number or part name and characteristic. For more information, see Short Run Process specifications