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The root mean square (abbreviated RMS or rms), also known as the quadratic mean, in statistics is a statistical measure defined as the square root of the mean of the squares of a sample. RMS can also be calculated for a continuously varying function. In physics it is a characteristic of a continuously varying quantity, such as a cyclically alternating electric current, obtained by taking the mean of the squares of the instantaneous values during a cycle. It is equal to the value of the direct current that would produce the same power dissipation in a resistive load.〔 This is a result of Joule's first law, which states that the power in resistive load is proportional to the square of the current (and, as a consequence of Ohm's law, also to the square of the voltage). The name ''root mean square'' is simply a description: the square root of the arithmetic mean of the squares of the samples. It is a particular case of the generalized mean, with exponent 2. ==Definition== The RMS value of a set of values (or a continuous-time waveform) is the square root of the arithmetic mean of the squares of the values, or the square of the function that defines the continuous waveform. In the case of a set of ''n'' values , the RMS : The corresponding formula for a continuous function (or waveform) ''f(t)'' defined over the interval is : and the RMS for a function over all time is : The RMS over all time of a periodic function is equal to the RMS of one period of the function. The RMS value of a continuous function or signal can be approximated by taking the RMS of a series of equally spaced samples. Additionally, the RMS value of various waveforms can also be determined without calculus, as shown by Cartwright. In the case of the RMS statistic of a random process, the expected value is used instead of the mean. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「root mean square」の詳細全文を読む スポンサード リンク
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