| random sampling | A selection of elements by a formal randomizing device for purposes of inference about a population of inference from that population in such a way that the probability of each possible outcome may be precisely specified in advance; the inferences are necessarily stochastic. (05 Mar 2000) |
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| random variable | A variable that may assume a set of values, each with fixed probabilities or probability densities (its distribution), in such a way that the total probability assigned to the distribution is unity; the random variable may be discrete, continuous, or mixed discrete-continuous. (05 Mar 2000) |
| random walk | <cell biology> A description of the path followed by a cell or particle when there is no bias in movement. The direction of movement at any instant is not influenced by the direction of travel in the preceding period. If changes of direction are very frequent, then the displacement will be small, unless the speed is very great and the object will appear to vibrate on the spot. Although the behaviour of moving cells in a uniform environment can be described as a random walk in the long term, this is not true in the short term because of persistence. (18 Nov 1997) |
| random waves | Wave's in the electroencephalogram which occur paroxysmally and asynchronously. (05 Mar 2000) |
| randomisation | <statistics> The process by which patients in a clinical trial are randomly assigned to different treatments Randomisation minimizes the differences among groups by equally distributing people with particular characteristics among all the trial arms. (09 Oct 1997) |
| randomised controlled trial | A clinical trial that involves at least one test treatment and one control treatment, concurrent enrollment and follow-up of the test- and control-treated groups, and in which the treatments to be administered are selected by a random process, such as the use of a random-numbers table. Treatment allocations using coin flips, odd-even numbers, patient social security numbers, days of the week, medical record numbers, or other such pseudo- or quasi-random processes, are not truly randomised and a trial employing any of these techniques for patient assignment is designated simply a controlled clinical trial. (12 Dec 1998) |
| randomised controlled trials | Clinical trials that involve at least one test treatment and one control treatment, concurrent enrollment and follow-up of the test- and control-treated groups, and in which the treatments to be administered are selected by a random process, such as the use of a random-numbers table. Treatment allocations using coin flips, odd-even numbers, patient social security numbers, days of the week, medical record numbers, or other such pseudo- or quasi-random processes, are not truly randomised and trials employing any of these techniques for patient assignment are designated simply controlled clinical trials. (12 Dec 1998) |
| randomised trial | <statistics> A clinical trial in which patients have been randomly assigned to receive either the study drug or alternative treatment, in which neither the patient nor the physician conducting the study know which treatment is being given the patient, and in which the alternative to the study drug is a placebo, the study is conducted at several centres. (09 Oct 1997) |
| randomization | Allocation of individuals to groups, e.g., for experimental and control regimens, by chance. (05 Mar 2000) |
| Raney alloy | An alloy of Ni and Al in equal proportions, used in the preparation of Raney Nickel. (05 Mar 2000) |
| Raney catalyst | Proprietary name for a finely powdered nickel catalyst made from Raney alloy by dissolving out the aluminum with alkali; used in the hydrogenation of organic substances. Synonym: Raney catalyst. (05 Mar 2000) |
| Raney Nickel | Proprietary name for a finely powdered nickel catalyst made from Raney alloy by dissolving out the aluminum with alkali; used in the hydrogenation of organic substances. Synonym: Raney catalyst. (05 Mar 2000) |
| range | The set of conditions throughout which an organism (for example, plant species) naturally occurs. (09 Oct 1997) |
| range of accommodation | The distance between an object viewed with minimal refractivity of the eye and one viewed with maximal accommodation. (05 Mar 2000) |
| range of convergence | The distance between the near point and far point of convergence. Synonym: range of convergence. (05 Mar 2000) |