Originally Posted by
ezwind72 So I got this problem wrong and again, I don't know why. If anyone can show me the right way to do it, I would be very appreciative.
The waiting time x at a fast-food restaurant during lunch time is approximately normally distributed with a mean of 4.5 min and a standard deviation of 1.2 min.
Find the value of the 75th percentile for x (in minutes).
I came up with 0.67 minutes and it was wrong. What I did was I drew my graph. I shaded in 75% (50% on the left and 25% on the right). I then looked up in the chart the closes z number to 0.2500 and got 0.67. I am not sure what I did wrong.