Average and standard deviation functions

stddev.mjs

// To use in the Node.js REPL:
// const { getAverage, getStandardDeviation } = await import("./stddev.mjs");

// @ts-check
export function getAverage(...values) {
  return values.reduce((sum, value) => sum + value, 0) / values.length;
}
export function getStandardDeviation(...values) {
  const average = getAverage(...values);
  const squaredDifferences = values.map((value) =>
    Math.pow(value - average, 2)
  );
  const variance = getAverage(...squaredDifferences);
  return Number(Math.pow(variance, 0.5).toFixed(2));
}

// Tests:
// getAverage(2, 1, 3, 2, 4) should be 2.40
// getStandardDeviation(2, 1, 3, 2, 4) should be 1.01