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G regression calculation methods, Appendix g, Regression calculation methods – Bio-Rad Image Lab™ Software User Manual

Page 229: Appendix g, regression calculation methods, Regression, To lear, Gregression calculation methods

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User Guide

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G

Regression Calculation

Methods

Each regression method calculates a standard curve. Some of the methods provide

the formula for the standard curve. In this case, the molecular weight can be

calculated by:

x = relative front of the band of interest

y = molecular weight of the band of interest

Linear (semilog): The linear equation is y = a + bx, where a is the intercept and b is

the slope of the line.

Note:

The linear equation is calculated on the log of the molecular weight

values.

The R

2

value can be used to determine the overall quality of the linear fit. A linear

regression with an R2 value of >0.99 is considered a very good fit. The primary

advantage of this method is that it is extremely simple. The primary disadvantage is

that it will deliver incorrect results if the data are not very linear.

Point-to-point (semilog): No single equation is available for the point-to-point

method. The slope of each segment of the curve between data points is calculated

independently.

Note:

The log of the molecular weight values is used to calculate the slope for

each segment of the curve.

Logistic: The logistic-4PL equation is

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