/guava/guava/src/com/google/common/math/PairedStats.java
return sumOfProductsOfDeltas / ( count ( ) - 1 ) ;
public double populationCovariance() { checkState(count() != 0); return sumOfProductsOfDeltas / count(); } public double sampleCovariance() { checkState(count() > 1); <extra_id_0> } public double pearsonsCorrelationCoefficient() { checkState(count() > 1); if (isNaN(sumOfProductsOfDeltas)) { return NaN; }