public double getStandardDeviation() {
        if (count == 0) {
            return 0;
        } else {
            double variance = (sumOfSquared - sum * sum / count) / count;
            return Math.sqrt(variance);
        }
    }
Constructor used for deserialization. Will be instantiated with a default sketch.
searchlib/src/main/java/com/yahoo/searchlib/aggregation/StandardDeviationAggregationResult.java