power

1. In optics, the refractive vergence of a lens. 2. In physics and engineering, the rate at which work is done. 3. The exponent of a number or expression that provides the number of times that number has to be multiplied by itself.

- back vertex p. the effective p. of a lens as measured from a surface toward the eye; a standard for measurement of ophthalmic lenses.

- carbon dioxide combining p. a measurement of the total CO₂ that can be bound as HCO₂ at a PCO₂ of 40 mmHg at 25°C by serum, plasma, or whole blood.

- equivalent p. the p. equal to an infinitely thin lens as measured on an optical bench.

- resolving p. 1. definition of a lens; in a microscope objective lens it is calculated by dividing the wavelength of the light used by twice the numerical aperture of the objective. SEE ALSO: definition. 2. analogies to other modalities, e.g., two-point discrimination in neurologic examination. Commonly misinterpreted as random error, although it has none of its properties. 3. SYN: resolution (2).

- statistical p. in Neyman-Pearson hypothesis testing, the probability of rejecting the null hypothesis when it is false; the complement of an error of the second kind.

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pow·er 'pau̇(-ə)r n

1) an inherent property or effect <a drug that enhances the heart's pumping \power (Kathleen Fackelmann)>

2) MAGNIFICATION (2b)

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pow·er (pouґər) [L. posse to have power] 1. capability; potency; the ability to act. 2. a measure of magnification, as of a microscope. 3. the rate at which work is done. Symbol P. The SI unit of power is the watt. 4. of a statistical test: the probability of correctly rejecting the null hypothesis when a specified alternative holds true; it is equal to 1 minus the probability of a Type II error.