When in doubt, look at the source:
/**
* Uses an exponentially decaying sample of 1028 elements, which offers a 99.9% confidence
* level with a 5% margin of error assuming a normal distribution, and an alpha factor of
* 0.015, which heavily biases the sample to the past 5 minutes of measurements.
*/
BIASED {
@Override
public Sample newSample() {
return new ExponentiallyDecayingSample(DEFAULT_SAMPLE_SIZE, DEFAULT_ALPHA);
}
};
A biased histogram is one that gives more weight to more recent measurements.