Figure of merit

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A Figure of merit is a quantity used to characterize the performance of a device relative to other devices of the same type. In engineering, figures of merit are often defined for particular materials or devices in order to determine their relative utility for an application. In commerce, such figures are often used as a marketing tool to convince consumers to choose a particular brand.

[edit] Examples

• Clock rate of a CPU
• Contrast ratio of an LCD
• Frequency response of a speaker
• Fill factor of a solar panel
• Resolution of the CCD in a digital camera
• Detection performance of a sonar system
• The thermoelectric figure of merit, Z, a material constant proportional to the efficiency of a thermoelectric couple made with the material
• The figure of merit of digital-to-analog converter(DAC) is calculated as (Power dissipation)/((2^ENOB) * Effective Bandwidth) [J/Hz].

[edit] Deception

A number quoted as a figure of merit may not be enough to determine performance when comparing products, yet consumers may solely depend on this number for selection. For example, when purchasing a laptop a consumer could choose based on the capacity of its hard drive. The rpm, cache, and seek times may not be notated, but significantly affect performance.

Another example is the megapixel count on digital cameras. The average consumer does not realize that the number of pixels on a sensor is only one indication of the quality of the image that is captured. In particular, more pixels can be squeezed onto the same-size sensor, which means a degradation of quality because the pixels are necessarily smaller.