So I have two known points on a normal distribution. A 50th percentile point and a 75th percentile point. How can I figure out what percentile a third point is at?
For instance: 50th percentile: 588.92 75th percentile: 719.92 xth percentile: 725.02
An excel/libreoffice calc formula would be fantastic, if possible.
HINT... The $50$th percentile is the mean $\mu$. You need to find $\sigma$, so get hold of a set of inverse $\Phi$ tables and use $\frac{712.92-\mu}{\sigma}=\Phi^{-1}(0.75)$. Can you take it from there?