Bell curve

[MLEBOFSKY]

Assume a bell curve. If I am given the 25th and 50th percentile values, how do I calculate the 30th percentile?
Example: 25th percentile salary is 60,000 dollars. 50th percentile salary is 80,000 dollars. What is the 30th percentile salary?
Not looking for the answer, looking for the equation.

THANKS

[Guest]

The basic "bell shaped curve" is [tex]y= e^{-x^2}[/tex]. Its mean is 0 and standard deviation is 1.
The general "bell shaped curve" is [tex]y= e^{\frac{(x- \mu)^2}{\lambda^2}}[/tex]. Its mean is [tex]\mu[/tex] and its standard deviation is [tex]\lambda[/tex].

Look up the "z" values corresponding to the 25th percentile and 50th percentile in a table of the standard normal distribution (there is one at https://www.bing.com/images/search?view ... ajaxserp=0)
Put those z values in [tex]\frac{z- \mu}{\lambda}= 60000[/tex] and [tex]\frac{z- \mu}{\lambda}= 80000[/tex] to get two equations to solve for [tex]\mu[/tex] and [tex]\lambda[/tex].