Suppose that the measured voltage in a certain electric circ

Suppose that the measured voltage in a certain electric circuit has a normal distribution with mean 120 and standard deviation 2. What is the probability that a measurement will lie between 116 and 118?

Solution

The probability is

P(116 <X< 118) = P((116-120)/2 <(X-mean)/s <(118-120)/2)

=P(-2<Z<-1)

=0.1359 (from standard normal table)