i've got a series of values (calibration standards) and have made a line of
best fit with them os area ratio against drug concentration, now i need to
use this line to establish the concentration of unknowns from their area ratio

thanks!

Extrapolation is dangerous. Interpolation is okay. You can use an algorithm
that interpolates between the two nearest points of the calibration, or an
algorithm that determines the concentration based on a best fit (regression)
of the entire calibration curve. Using the regression is somewhat easier.
The unknown Y value is given by:

=TREND(Y-range,X-range,X-value)

Where Y-range and X-range are the ranges with the fitted Y and X values, and
X-value is the value of X at which you want to calculate Y.

- Jon
-------
Jon Peltier, Microsoft Excel MVP
Tutorials and Custom Solutions
Peltier Technical Services, Inc. - http://PeltierTech.com
_______



"lucybelle" wrote in message
...
i've got a series of values (calibration standards) and have made a line
of
best fit with them os area ratio against drug concentration, now i need to
use this line to establish the concentration of unknowns from their area
ratio

thanks!