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#1
Posted to microsoft.public.excel.charting




How can i extrapolate and find/show values on a calibration curve
Im am writing the scientific report where I have a calibration curve. I want
to use that and find the concentration of an unknown sample. This is easily done by hand, but how do i show it on exel and on the chart itself? 
#2




Answer: How can i extrapolate and find/show values on a calibration curve
To extrapolate and find/show values on a calibration curve in Excel, you can follow these steps:
By following these steps, you can easily extrapolate and find/show values on a calibration curve in Excel and display them on your chart.
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#3
Posted to microsoft.public.excel.charting




How can i extrapolate and find/show values on a calibration curve
I will assume that the calibration curve is linear (y = mx + b)
In some cell (say D1) we can find the slope (m) with the formula =SLOPE(yvalues, xvalues) Something like =SLOPE(B2:B12, A2:A12) Likewise in say D2 we can find intercept (b) with =INTERCEPT(yvalues, xvalues) Let D3 contain the measured yvalue from which you need to compute its xvalue Let these values be Y and X So Y =mX + b or X = (Yb)/m Turning this into Excel: in cell D4 enter =(D3D2)/D1 Now having done that, you need to be able to report also your confidence intervals See http://people.stfx.ca/bliengme/Excel...onfidence3.htm By the way: I hope you are INTERPOLATING for the calibration curve not EXTRAPOLATING The former is generally valid, while the later is fraught with dangers best wishes  Bernard V Liengme Microsoft Excel MVP http://people.stfx.ca/bliengme remove caps from email "Heekla" wrote in message ... Im am writing the scientific report where I have a calibration curve. I want to use that and find the concentration of an unknown sample. This is easily done by hand, but how do i show it on exel and on the chart itself? 
#4
Posted to microsoft.public.excel.charting




How can i extrapolate and find/show values on a calibration curve
Hi,
Following on from Bernard, once you've found the x and y values for your sample, just plot them as a new series on the chart. You can also add x and y error bars linking the point with each axis if you want to do it like in the "old days" when we used graph paper. Obviously, it looks better if you've removed the lines between the data points and added a suitably formatted (preferably linear)trendline to the chart. If you've done the calculations properly, you should see your new sample point sitting on the trendline. Don't be tempted to apply some higher order polynomial trendline just because it looks to fit the data better. Dave url:http://www.ureader.com/msg/10297359.aspx 
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