# Thread: I need help with this one!

1. ## I need help with this one!

A manufacturer needs coil springs that can stand a load of at least 20.0 pounds. The supplier can provide coil springs that, on average, can stand a load of 24.5 pounds with a standard deviation of 2.1 pounds. If we can assume that the distributions of these loads can be approximated with normal distributions, determine the percentage of unsatisfactory coil springs that would be obtained from the supplier.

I am having a difficult time with this one. Can anyone help?

2. so your mean would be 24.5, and we are interested in the area below 20, so you would have:

$\displaystyle \frac{20-24.5}{2.1} = 2.1429$

$\displaystyle P(Z=2.1429) =0.0166$

so 0.0166 coils would be inadequate

3. Originally Posted by lllll
so your mean would be 24.5, and we are interested in the area below 20, so you would have:

$\displaystyle \frac{20-24.5}{2.1} = 2.1429$

$\displaystyle P(Z=2.1429) =0.0166$

so 0.0166 coils would be inadequate
Don't forget to multiply 0.0166 by 100 to get the percentage !

P.S. I think it's 0.01606 .....