| correlation coefficient | A measure of association that indicates the degree to which two variables have a linear relationship; this coefficient, represented by the letter r, can vary between +1 and -1; when r = +1, there is a perfect positive linear relationship in which one variable relates directly with the other; when r = -1, there is a perfect negative linear relationship between the variables. (05 Mar 2000) |
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| rank-difference correlation | The relationship between paired series of measurements, each ranked according to magnitude, which yields a coefficient known as rho; the value of rho varies from zero (no relationship) to +1.00 (perfect relationship). (05 Mar 2000) |
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| correlation | <statistics> most generally, the degree to which one phenomenon or random variable is associated with or can be predicted from another. In statistics, correlation usually refers to the degree to which a linear predictive relationship exists between random variables, as measured by a correlation coefficient. Correlation may be positive, i.e., both variables increase or decrease together or negative or inverse, i.e., one variable increases when the other decreases. (18 Nov 1997) |
| product-moment correlation | A statistical procedure which yields the correlation coefficient referred to as r (-1.00 to +1.00) and involves the actual values, rather than the ranks (rank order) of the measurements. (05 Mar 2000) |
| absorption coefficient | <physics> Measures the degree of wave absorption defined as the fraction of wave energy lost as the wave travels a unit distance. See: absorption. (15 Jan 1998) |
| activity coefficient | <chemistry> The factor by which the value of a concentration of a solute must be multiplied to determine its true thermodynamic activity. (06 May 1997) |
| attenuation coefficient | 1. <radiobiology> Compton: The fractional number of photons removed from a beam of radiation per unit thickness of material through which it is passing as a result of Compton effect interactions. 2. Linear: The fractional number of photons removed from a beam of radiation per unit thickness of material through which it is passing due to all absorption and scattering processes. 3. Pair Production: That fractional decrease in the intensity of a beam of ionising radiation due to pair production in a medium through which it passes. 4. Photoelectric Effect: That fractional decrease in the intensity of a beam of ionising radiation due to photoelectric effect in a medium through which it passes. (16 Dec 1997) |
| biological coefficient | Rarely used term denoting the energy expended by the body at rest. (05 Mar 2000) |
| Bunsen's solubility coefficient | The milliliters of gas STPD dissolved per milliliter of liquid and per atmosphere (760 mm Hg) partial pressure of the gas at any given temperature. (05 Mar 2000) |
| velocity coefficient | The rate of transformation of a unit mass of substance in a chemical reaction. (05 Mar 2000) |
| recombination coefficient | <radiobiology> The rate of recombination of positive ions with electrons (or negative ions) in a gas, per unit volume, divided by the product of the particle densities of the two species (positive ions and electrons/negative ions) involved. (09 Oct 1997) |
| mass attenuation coefficient | <physics> The mass attenuation coefficient, u/p, of a material for uncharged ionising particles is the quotient of DN/N by pdl, where DN/N is the fraction of particles that experience interactions in traversing a distance dl in a material of density p. (16 Dec 1997) |
| mass energy absorption coefficient | <physics> The mass energy absorption coefficient, uen/p of a material for uncharged ionising particles is the product of the mass energy transfer coefficient, utr/p and (1 - g) where g is the fraction of the energy of secondary charged particles that is lost to bremsstrahlung in the material. (16 Dec 1997) |
| reflection coefficient | A measure of the relative permeability of a particular membrane to a particular solute; calculated as the ratio of observed osmotic pressure to that calculated from van't Hoff's law; also equal to 1 minus the ratio of the effective pore areas available to solute and to solvent. (05 Mar 2000) |
| partition coefficient | <chemistry> Equilibrium constant for the partitioning of a molecule between hydrophobic (oil) and hydrophilic (water) phases. A measure of the affinity of the molecule for hydrophobic environments and thus, for example: a rough guide to the ease with which a molecule will cross the plasma membrane. (18 Nov 1997) |
| reliability coefficient | An index of the consistency of measurement often based on the correlation between scores obtained on the initial test and a retest (test-retest reliability) or between scores on two similar forms of the same test (equivalent-form reliability). (05 Mar 2000) |