What are the odds?

Q: What is the success rate for IUI?

I am so confused by this question! I can't seem to find an answer that makes sense! This is what I found...

A: Searching through about a dozen medical journal articles and a number of web sites resulted in a rather wide range of statistics. Basically the odds of success are reported to be just under 6 percent and as high as 26 percent per cycle. The low statistics are with one follicle, while multiple follicles resulted in as high 26 percent success. Another influencing factor is sperm count. Higher sperm counts increase the odds of success; however, there was little difference between success with good-average counts and those with high counts. The overall success rate seems to be between 15-20 percent per cycle, judging from the articles which will be abstracted below. The rate of multiple gestation pregnancies is 23-30 percent.

There is a 25% to 30% chance of conceiving in any given cycle without medical intervention.

So this is where I get lost. If my chances are 25-30% on a natural cycle, then why do they drop to possibly 6% with a IUI? I guess that factors infertility in... I'm confused. I just need to trust in God and forget about the numbers... it only takes one, right?!