1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
import sumNthPowerDeviations from "./sum_nth_power_deviations";
/** * The [sample variance](https://en.wikipedia.org/wiki/Variance#Sample_variance) * is the sum of squared deviations from the mean. The sample variance * is distinguished from the variance by the usage of [Bessel's Correction](https://en.wikipedia.org/wiki/Bessel's_correction): * instead of dividing the sum of squared deviations by the length of the input, * it is divided by the length minus one. This corrects the bias in estimating * a value from a set that you don't know if full. * * References: * * [Wolfram MathWorld on Sample Variance](http://mathworld.wolfram.com/SampleVariance.html) * * @param {Array<number>} x a sample of two or more data points * @throws {Error} if the length of x is less than 2 * @return {number} sample variance * @example * sampleVariance([1, 2, 3, 4, 5]); // => 2.5 */function sampleVariance(x) {    if (x.length < 2) {        throw new Error("sampleVariance requires at least two data points");    }
    const sumSquaredDeviationsValue = sumNthPowerDeviations(x, 2);
    // this is Bessels' Correction: an adjustment made to sample statistics    // that allows for the reduced degree of freedom entailed in calculating    // values from samples rather than complete populations.    const besselsCorrection = x.length - 1;
    // Find the mean value of that list    return sumSquaredDeviationsValue / besselsCorrection;}
export default sampleVariance;