When joining two StatCalucators (where a key in the TreeMap has value > 1) I got incorrect values of the final dataset (count, sum, deviation ..) 

Problematic functions are addAll(StatCalculator<T> calc) and addValue(T val, int sampleCount)

See example showing the behavior and proposed fix of the functions.

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EXAMPLE
Let’s have two StatCalculator sc1 and sc2. 
sc1 has values: 1, 2, 3
sc2 has values: 2, 2, 2

STAT.VALUES OF sc1 
count: 3
sum: 6.0
deviation: 0.8164965809277263
TreeMap: 
• key: 1 value: 1
• key: 2 value: 1
• key: 3 value: 1

STAT.VALUES OF sc2 
count: 3
sum: 6.0
deviation: 0.0
TreeMap: 
• value: 2 count: 3

STAT.VALUES OF sc1+sc2  (sc1.addAll(sc2))
count: 4   WRONG (should be 6)
sum: 8.0   WRONG (should be 12)
deviation: 0.707106711865476 WRONG (should be 0.5773502691896255)
TreeMap: 
• key: 1 value: 1
• key: 2 value: 2 WRONG(samples with response=2ms occurs 4times!)                  
• key: 3 value: 1

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ORIGINAL FUNCTIONS:

public void addAll(StatCalculator<T> calc) {
        for (T val : calc.valuesMap.keySet()) {
            addValue(val);
        }
    }

public void addValue(T val, int sampleCount) {
        count += sampleCount;
        double currentVal = val.doubleValue();
        sum += currentVal;
        T actualValue = val;
        if (sampleCount > 1){
            // For n values in an aggregate sample the average value = (val/n)
            // So need to add n * (val/n) * (val/n) = val * val / n
            sumOfSquares += currentVal * currentVal / sampleCount;
            actualValue = divide(val, sampleCount);
        } else {
            sumOfSquares += currentVal * currentVal;
            actualValue = val;
        }
        updateValueCount(actualValue, sampleCount);
        mean = sum / count;
        deviation = Math.sqrt((sumOfSquares / count) - (mean * mean));
        if (actualValue.compareTo(max) > 0){
            max=actualValue;
        }
        if (actualValue.compareTo(min) < 0){
            min=actualValue;
        }
    }
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FIXED FUNCTIONS:

public void addAll(StatCalculator<T> calc) {
        for (T val : calc.valuesMap.keySet()) {
        	addValue(val , calc.valuesMap.get(val).intValue());
        }
    }


public void addValue(T val, int sampleCount) {
        count += sampleCount;
        double currentVal = val.doubleValue();   
        sum += currentVal * sampleCount; 
        // For n same values in sum of square is equal to n*val^2
        sumOfSquares += currentVal * currentVal * sampleCount; 
        updateValueCount(val, sampleCount);       
        mean = sum / count;
        deviation = Math.sqrt((sumOfSquares / count) - (mean * mean));
        if (val.compareTo(max) > 0){
            max=val;
        }
        if (val.compareTo(min) < 0){
            min=val;
        }
    }