I'm looking at an example. There's one part that I don't understand.
The random variable Y has a normal distribution with mean 10 and standard deviation 2. Find the value of the constant a such that P(10-a<Y<10+a)=0.95.
What I don't get it is how does P(10-a<Y<10+a)=0.95
gives me P(Y<10-a)=0.025 ???
Any help is much appreciated. Thanks.