Engineering Tables/Normal Distribution/Tail Function Graph

The tail function is the area under the normal distribution N(0,1) between x and +∞:

$\text{T}(x)=\underset{x}{\overset{\mathrm{\infty }}{\int }}\frac{1}{\sqrt{2\pi }}\exp \left(-\frac{y^2}{2}\right)dy$

For x > 6.5, the tail function can be approximated as:

$\text{T}(x)=\frac{1}{x\sqrt{2\pi }}\exp \left(-\frac{x^2}{2}\right)$