I need help with problem 2. I know I have to use the Z table and stuff.

The mean is 27 and standard deviation is 9.

For part A and B, am i suppose to solve for x?

I;m not sure on how to approach it

For parts a and b, the 85th percentile is equivalent to 0.85 and 20th percentile is equivalent to 0.20. From here, look up on the z-table what z-scores correspond to each 0.85 and 0.20. Then use the formula x = mu + z * sigma to determine the speed for each percentile.

okay thanks man. when I look up the Z table, which one do I use since there are variations of it depending on which area you are lookin at it.

I'm assuming, use the one where the area is shaded from the left to right?

SO ACCORDING TO THE ztable, the 85th percentile would correspond to z = 1.04, correct me if I am wrong

http://www.stat.ufl.edu/~athienit/Tables/Ztable.pdf

This post was edited by FamilyGuyViewer on Feb 22 2015 01:52pm

x = (1.04)(9) + 27 = 36.36

is this right?

also need help with #3.

im getting negative numbers when I use the formula in the picture.
I used r= 12/(1*5) where lamba = 12 and mu is 5

That should be correct.

I'm unfamiliar with Poisson distribution so feanur or saberx3 or another may need to help here.