Figure of merit

A figure of merit is a quantity used to characterize the performance of a device, system or method, relative to its alternatives.

Benchmarks are synthetic figures of merit that summarize the speed of computers in performing various typical tasks.

In modulation systems for communication, figure of merit of a device means the ratio of output signal to noise ratio ((SNR)_O) to the input signal to noise ratio ((SNR)_C).

Figure of merit for amplitude modulation (AM) is given by

Figure of merit for double-sideband suppressed-carrier (DSB-SC) receiver or that of a single-sideband (SSB) modulation is always unity. Therefore, noise performance of AM receiver is inferior to that of a DSB-SC receiver or an SSB receiver.

Figure of merit for frequency modulation is given by

The precision and verifiability of numbers sometimes make them a more effective sales tool than vague and non-numeric descriptions such as "state of the art" or "leaves the others in the dust". When used in deceptive advertising, the deception lies more in the question of relevance rather than truth since the number quoted, as a figure of merit may not be enough to determine performance when comparing products. For example, when purchasing a laptop a consumer could choose on the basis of the capacity of its hard drive. The RPM, buffer, and seek times may not be noted, but may significantly affect performance.

Some figures such as peak music power are used in selling consumer merchandise and have the principal merit of yielding high numbers that can impress people who don't know what the numbers mean. Other figures such as specific fuel consumption are addressed to engineers and other studious buyers whom the sellers dare not mislead.

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