# Use Lognormal Distribution

The lognormal distribution has two parameters, μ and σ. These are not the same as mean and standard deviation, which is the subject of another post, yet they do describe the distribution, including the reliability function.

$\displaystyle R(t)=1-\Phi \left( \frac{\ln (t)-\mu }{\sigma } \right)$

Where Φ is the standard normal cumulative distribution function, and t is time. Continue reading Use Lognormal Distribution