Assume the random variable X is normally distrubted with mean = 50 and standard deviation = 7. Compute its probability.
P(34 < X < 61)?
P(34 < X < 61) =
P( X = 61) - P( X = 34)
Using the formula Z = (X - Mean)/Std Deviation
(61 - 50)/ 7 = 1.57
(34 - 50)/7 = -2.28
ɸ(1.57) - ɸ(-2.28)
ɸ(-2.28) = 1-ɸ(2.28)
As CB mentioned ɸ basically means look it up from a standard normal distribution table
Hope this helps