Maths Statistics Questions

Q1) X~N(a,a^2)
Given that P(X<3) = 0.2, find the value of a.

Q2) X~N(57,10^2) is the model for student's marks
4.5% fail so work out the minimum pass mark.

Hello.

Here is the answer to your questions.

Part 1: http://www.flickr.com/photos/61918355@N0…
Part 2: http://www.flickr.com/photos/61918355@N0…

I hope I've been of some help. Good luck.

inverse normal (0.2) = -0.84 ---> (3-a)/a = -0.84 ----> a = 19

2/
inverse normal (0.045) = -1.70 ---> (x-57)/10 = -1.7 --->X = 47