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// 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