The probability p(x > 0) is

Direction: for the probability of a Gaussian variable x is given by

P_x(x) =	1	e^{– (x – 4)²/18}
	3√2π

Q. (0) = 0·5, Q		4		= 0·09176
		3

and Q. (2) = 0·02275

P(x > 4) = Q		0 - 4		= Q		– 4
		3				3

= 1 – Q		4
		3

= 1 – 0·09176
= 0·90824