Daisy discovers that the amount of time it takes her to drive to work is normally with:?

mean of 30 minutes and a standard deviation of 7 minutes. At what time should Daisy leave her home so that she has a 90 % chance of arriving at work by 9 AM ?

Daisy discovers that the amount of time it takes her to drive to work is normally with:?
Let t = time it actually takes her to get to work



Then t ~ N(30, 7^2)



Let T = amount of time before 9AM that she would like to leave home.



We wish to find T such that P(t%26lt;T) = 0.9

or P(z %26lt; [T-30]/7) = 0.9



Looking at the normal distribution tables,

This z value = 1.28

So (T-30)/7 = 1.28

T = 39 mins.



She must leave 39 mins before 9 AM to have a 90% chance of being at work on time.
Reply:Deviation is 7. Meaning -7 should leave by 8:30. Subtract by -7. Answer 8:23.