平均大小为 3,131 平方英尺，标准偏差为 655 平方英尺（标准偏差是一个描述差异的统计量度）。
The average size is 3,131 square feet, with a standard deviation of 655 square feet. (Standard deviation is a statistical measure of variance.)
那个时候，大多数的计量单位都是来源于实物、手、人体部位（比如“英尺”的英文原意为脚，英里则来源于拉丁语的milia passuum，意为1000步）或者工具（比如桶、杯子）。
Most were drawn from things to hand: the human body (the foot or the mile, which derives from the Latin milia passuum, or 1, 000 paces) and tools (barrels, cups).
货币假定意味着美元具有同样的特征-时间稳定性-如同英尺、加仑等所有其他已经普遍接收的计量单位。
The monetary assumption implies that the (U. S.) dollar has the same characteristic_stability over time _as all other generally accepted measuring units such as the inch, gallon, etc.
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