small question, is there an equation that'll give you a graph like a bell curve?
Yes, there is:
The one used to calculate the standard normal table is:
$\displaystyle \frac{1}{\sqrt{2\pi}}\int_{-\infty}^{z}{e^{\frac{-x^{2}}{2}}}dx$
For instance, if you have a stats book with the table to compare for fun.
Try integrating the above with z=-1.645. You should get very close to 0.05.
Actually, it's 0.0499849....