// Just use the common formulas for standard deviation function stdDev(dataset, isPopulation) { let n = dataset.length; const mean = dataset.reduce((a, b) => a + b) / n; n = isPopulation ? n : (n - 1); return Math.sqrt(dataset.map(x => Math.pow(x - mean, 2)).reduce((a, b) => a + b) / n); } stdDev([1, 2, 4, 5, 9], true); // Returns ~2.786 stdDev([1, 3, 5, 7, 10, 11], false); // Returns ~3.920