public double getStdDev() {
        if (mustRecalcVariance || Double.isNaN(stddev)) {
            stddev = Math.sqrt(getVariance());
        }
        return stddev;
    }
Get the standard deviation of all increments that have been added
@return the standard deviation of all increments that have been added
benchmarks/src/main/java/nl/basjes/statistics/Counter.java