You can find my point of view about the exercise in annexe!
Random variable X ~ N(20,12)
Find the values of a and b:
P(X<a) = 0.40
P(X>b) = 0.6915
I can't get the answer in the text book and no worked examples are available. Any ideas would be greatly appreciated ...
My workings are:
P(X<a) = P(Z<((a-20)/(sqrt12)) using mu and sigma
P(Z<((a-20)/(sqrt12)) = 0.40
but dont have 0.4 in my Z tables.
tre same for the other equation.