# Thread: Normal Distribution

1. ## Normal Distribution

The diameter of an automobile tire is normally distributed , with a mean =575 mm and a stand-dev= 5mm.
1) what is probability that randomly selected tire has diameter
a) b/ween 575 mm and 579 mm
b) 572 and 580 mm
c) above 570 mm
d) below 580 mm

2)80 percent of the tires will have diameters above what value?
3) 80 percent of the tires will have diameters b/ween what two values (symmetrically distributed around the mean)?
4)Explain the diff b/w your answer to 2) and 3)
5) suppose that stand dev of the diameter is reduced to 0.04 mm. what would answers to a)- d) be.

I was having trouble figuring this problem out on excel... equations to how to do it on excel would be greatly appreciated!
THANK YOU IN ADVANCE!

2. Originally Posted by willdriver
The diameter of an automobile tire is normally distributed , with a mean =575 mm and a stand-dev= 5mm.
1) what is probability that randomly selected tire has diameter
a) b/ween 575 mm and 579 mm
b) 572 and 580 mm
c) above 570 mm
d) below 580 mm

2)80 percent of the tires will have diameters above what value?
3) 80 percent of the tires will have diameters b/ween what two values (symmetrically distributed around the mean)?
4)Explain the diff b/w your answer to 2) and 3)
5) suppose that stand dev of the diameter is reduced to 0.04 mm. what would answers to a)- d) be.

I was having trouble figuring this problem out on excel... equations to how to do it on excel would be greatly appreciated!
THANK YOU IN ADVANCE!
Do you know how to do these in principle? That is, what is the answer to 1a, you can leave it in terms on the standard normal CFD.

If you can't answer that your problem is not with Excel but with the concepts.

CB