public void isNormal(double mean, double stddev) {
			follows(new NormalDistribution(mean, stddev));
		}
Checks if the observation follows a normal distribution with the
given {@code mean} and standard deviation.

@param mean the mean value of the expected normal distribution
@param stddev the standard deviation of the expected normal
       distribution
jenetics.incubator/src/main/java/io/jenetics/incubator/stat/Assurance.java