| Section S | S index | 391-399 of 1376 terms |
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significance testA test of the reliability of estimate of statistical parameters. Such tests proceed by assuming that the estimates are not significant and are those to be expected from sampling a particular population, and then, from the properties of the population, determining the probabilities of such occurrences. The hypothesis (that the estimates are not significant) is rejected only when an observational result is found to be significant, that is, when the obtained result belongs to an objectively specified unfavorable class (critical region or rejection region) having a fixed, small probability of occurrence in random samples from the hypothesized population. When the result falls in the acceptance region, it is not significant and the hypothesis cannot be rejected. The boundaries of the classes are set in such a way that the total probability (unity) is appropriately divided between them, say 0.95, 0.05 or 0.99, 0.01. The probability assigned to the critical region, commonly either 0.05 or 0.01, is called the significance level. See chi- square test, Student's t-test, analysis of variance.
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significant levelIn a radiosonde observation, a level (other than a mandatory level) for which values of pressure, temperature, and humidity are reported because temperature and/or moisture- content data at that level are sufficiently important or unusual to warrant the attention of the forecaster, or they are required for the reasonably accurate reproduction of the radiosonde observation.There are definite rules governing the selection of significant levels, set forth in the Manual of Radiosonde Observations, WBAN Circular P, 7th ed. rev., 1957.
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significant wave heightDefined traditionally as the mean height of the highest third of the waves, but now usually defined as four times the root-mean-square of the surface elevation (or equivalently as four times the square root of the first moment of the wave spectrum).
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significant waveIn ocean wave forecasting, a fictitious wave with a height and period equal to the average height and period of the highest one-third of the actual waves that pass a fixed point.
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significant weather chartChart displaying the observed or forecast significant weather phenomena at different flight levels that may affect the operation of the aircraft.
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significant weatherIn aviation weather, the occurrence or expected occurrence of specified en route weather phenomena that may affect the operation of aircraft.
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siguaA straight-blowing monsoon gale of the Philippines.
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