final boolean sameState(final MomentStatistics statistics) {
		return _n == statistics._n &&
			_m1.sameState(statistics._m1) &&
			_m2.sameState(statistics._m2) &&
			_m3.sameState(statistics._m3) &&
			_m4.sameState(statistics._m4);
	}
Return the kurtosis of values recorded, or {@code Double.NaN} if less
than four values have been recorded.

@see <a href="https://en.wikipedia.org/wiki/Kurtosis">Kurtosis</a>

@return the kurtosis of values, or {@code NaN} if less than four values
        have been recorded
jenetics/src/main/java/io/jenetics/stat/MomentStatistics.java