1. Suppose you record how long it takes you to get to work over many months and discover that the times are approximately normal with a mean of 15 minutes and a standard deviation of 2 minutes. How much time should you allow to get there to make sure you are on time 90% of the time? What I have done so far. I have set up model with the times 7, 9, 11, 15, 17, 19, 21 and made a normal distribution curve. I figured that about 90% would lie around 18. I know that I need to do something with the z-score table but I am a little cofused about what.