Hi, need guidance for this question! 1. During 2011, the number of flying hours for each SIA aircraft was normally distributed with mean 2389 and a standard deviation of 300.
So, What number of annual flying hours was exceeded by only 10% of the aircraft?

Question

Hi, need guidance for this question! 1.	During 2011, the number of flying hours for each SIA aircraft was normally distributed with mean 2389 and a standard deviation of 300. 
So, What number of annual flying hours was exceeded by only 10% of the aircraft?

amistre64 · Answer

do you have a ti83 or similar calculator?

anonymous · Answer

hmmmm, nope! is there any formula i could use?

anonymous · Answer

If not, then you'll need to know the Z-score formula and have a standard normal distribution table handy.

anonymous · Answer

http://stattrek.com/probability-distributions/standard-normal.aspx?Tutorial=AP http://www.math.unb.ca/~knight/utility/NormTble.htm

anonymous · Answer

but wait,how can i solve that 10%? any idea?

anonymous · Answer

That's the top 10%, which means that there is 90% (or P=0.9000) below that z-score.
Find the z-score that is associated with P≈0.9 and put that in the z-score formula to solve for x.

anonymous · Answer

Using the table, you'll have to do what is called a 'backwards lookup' - find the p-value in the body of the table then read across to the margins to find the z-score.

anonymous · Answer

alright thank you! i will try to solve!