Unfortunately the CDF function of the normal distribution is not known in closed form. Therefore to obtain those probabilities you need to use something else, such as the Q-function tables.

The Q-function is the complementary of the CDF of a standard normal distribution. "Standard" states for mean=0 and std=1, which is exactly what you have.

To know the probability P(z > 1.09) you simply go into the table (e.g. at the end of http://en.wikipedia.org/wiki/Q-function) and find the value of Q(1.09) = 0.1356. Since the standard normal distribution is symmetric, P(z < -1.09) = P(z > 1.09) = 0.1356. Since the events "z < -1.09" and "z > 1.09" are mutually exclusive, you have:
P(z < -1.09 or z >1.09) = P(z < -1.09) + P(z >1.09)

Hence finally,
P(z < -1.09 or z >1.09) = 2 P(z >1.09) = 2*Q(1.09) = 2*0.1356

Be careful thought that in case your normal distribution is not standard, you need to normalise the value 1.09 before going into the Q-function table. If you need to know this as well, comment my answer and I will update it.

View the original article here