11/19/2022 0 Comments Least squares regression excel![]() From the menu choose Chart/Add Trendline. Graph the data using a Scatter (XY) plot in the usual way. ![]() How do we do our second order fit using Excel? This tells us that doing a second order fit on these data should be professionally acceptable. Our results show (1.07/9.19)*100 = 12%.Ģ) We have been warned that at moderately high absorbance values we might get non-linearity when doing atomic absorption.ģ) Consulting the manual for our atomic absorption spectrometer, we find that it has built-in software for a "three-point calibration." Three points are the minimum needed to do a curved, second-order fit. Instead, we must rely on what a professional chemist would expect to see.ġ) We expect the error for this method to be around 1 or 2%. There is no reliable formula or computer analysis that can tell the difference between scattered data and curved data when the number of data points is small. How do we know that this is a poor choice? Do the data really have the amount of scatter shown? Shouldn't we just accept the value of 9.19 +or- 1.07 µg/mL? These questions do not have obvious answers. ![]() In the example above we see a standard LLS first order fit. A First Order Fit to the data used to construct a working curve follows the equation:įailure to check our data for linearity before performing our usual Linear Least Squares (LLS) analysis will generate a large error if the data are curved rather than straight. ![]()
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