In statistics, the theoretical curve that shows how often an experiment will produce a particular result. The curve is symmetrical and bell shaped, showing that trials will usually give a result near the average, but will occasionally deviate by large amounts. The width of the “bell” indicates how much confidence one can have in the result of an experiment — the narrower the bell, the higher the confidence. This curve is also called the Gaussian curve, after the nineteenth-century German mathematician Karl Friedrich Gauss. (See statistical significance.)
Note: The normal distribution curve is often used in connection with tests in schools. Test designers often find that their results match a normal distribution curve, in which a large number of test takers do moderately well (the middle of the bell); some do worse than average, and some do better (the sloping sides of the bell); and a very small number get very high or very low scores (the rim of the bell).
noun, Mathematics. 1. a normal subgroup.
noun, Statistics. 1. a value x such that the integral of a normal curve over all those values of the independent variable less than x is equal to the given probability.
noun, Geology. 1. . normal fault A geologic fault in which the hanging wall has moved downward relative to the footwall. Normal faults occur where two blocks of rock are pulled apart, as by tension. Compare reverse fault. See Note and illustration at fault.
- Normal form
1. In reduction systems, the state of a term which contains no reducible expressions. Variants include head normal form, weak head normal form. 2. See database normalisation.