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Variability.
In statistics, the Variance is the average of the squared differences from the Mean Value. In other words, the variance describes how far a set of numbers is Spread Out from the mean (average) value. Mean value is described in the previous chapter.
10 11 14 14 15
// Calculate the Mean (m)
let m = (7+8+8+9+9+9+10+11+14+14+15)/11;
// Calculate the Sum of Squares (ss)
let ss = (7-m)**2 + (8-m)**2 + (8-m)**2 + (9-m)**2 + (9-m)**2 + (9-m)**2 + (9-m)**2 + (10-m)**2 + (11-m)**2 + (14-m)**2 + (15-m)**2;
// Calculate the Variance let variance = ss / 11;Or use a math library like math.js
const values = [7,8,8,9,9,9,10,11,14,14,15];
let variance = math.variance(values, "uncorrected");Standard Deviation is a measure of how spread out numbers are.
Ï (Greek letter sigma).
√ variance (the square root of the variance). The Standard Deviation is (in JavaScript): // Calculate the Mean (m)
let m = (7+8+8+9+9+9+10+11+14+15)/11;
// Calculate the Sum of Squares (ss)
let ss = (7-m)**2 + (8-m)**2 + (8-m)**2 + (9-m)**2 + (9-m)**2 + (9-m)**2 + (9-m)**2 + (10-m)**2 + (11-m)**2 + (14-m)**2 + (15-m)**2;
// Calculate the Variance let variance = ss / 11;
// Calculate the Standard Deviation let std = Math.sqrt(variance);Distance.
(on average), all values are from the Mean (the Middle). Or if you use a math library like math.js
const values = [7,8,8,9,9,9,9,10,11,14,15];
let std = math.std(values, "uncorrected");