Standard deviation (Std Dev)-a statistical term. It is a standard to measure the dispersion of data distribution, which is used to measure the degree to which data values deviate from the arithmetic mean. The smaller the standard deviation, the smaller the deviation of these values from the average. or vice versa, Dallas to the auditorium The standard deviation can be measured by the ratio between the standard deviation and the average value. The standard deviation formula is S = Sqr(∑(xn-x dial) 2/(n- 1)). In the formula, ∑ stands for sum, x dial stands for arithmetic average of x, 2 stands for quadratic, and Sqr stands for square root.
Example: There is a set of numbers, which are 200, 50, 100, 200 respectively. Find their standard deviation.
X dial = (200+50+100+200)/4 = 550/4 =137.5.
s^2 =[(200- 137.5)^2+(50- 137.5)^2+( 100- 137.5)^2+(200- 137.5)^2]/(4- 1)
Standard deviation s = sqr (s 2)
STDEV estimates the standard deviation from the sample. The standard deviation reflects the dispersion degree of the numerical value relative to the average value.