âº EVC System. A disabled refuge is a relatively safe area within a building or exit staircase for mobility impaired occupants, allowing building management and emergency services to safely assist these people from the building.
Standard deviation is a number used to tell how measurements for a group are spread out from the average (mean), or expected value. A low standard deviation means that most of the numbers are very close to the average. A high standard deviation means that the numbers are spread out.
The standard deviation of a population is defined by the following formula: Ï = sqrt [ Ï (X i-X) 2 / N ]. where Ï is the population standard deviation, X is the population mean, X i is the i th element from the population, and N is the number of elements in the population. The standard deviation of a sample is defined by slightly different formula: s = sqrt [ Ï (x i-x) 2 / (n - 1) ]. where s is the sample standard deviation, x is the sample mean, x i is the i th element from the sample, and n is the number of elements in the sample. And finally, the standard deviation is equal to the square root of the variance.