I have unit test tomorrow and I'm not quite understanding how to do this question.

Question

cecil_the_weasel · Answer

attachment

ssddss02 · Answer

12 minutes

cecil_the_weasel · Answer

The answer (according to the textbook) is 59 minutes. 
12 minutes is not very close to the mean either; 13 standard deviations, actually.

kaylee04 · Answer

weird

rhondasommer · Answer

qualifying time = x

z = (x - 63)/4
P(z > (x - 63)/4) = 0.16
P(z > 0.9945)=0.16

So, (x - 63)/4 = 0.9945
or, x = 0.9945 *4 +63 = 66.978

minimum qualifying time = 67 min. (Ans.)

cecil_the_weasel · Answer

Thanks RhondaSommer :D
Your answer actually seems more likely than the textbook answer because the question asked for the top 16% and 59 is less than the mean.
Thanks for actually posting the steps to solve as well.
It really is surprising how many wrong answers are in my textbook.

rhondasommer · Answer

your totally welcome, I would have walked you through it but I was exhausted :P lmk if you ever have ay questions :)