power function and how it is calculated by Office Excel.

  • Thread starter Thread starter Mark Anthony Browne
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M

Mark Anthony Browne

Dear Group

I am trying to calibrate a load cell to measure forces. I was wondering
whether anyone could tell me how the power function is calculated by Office
Excel.
 
you can either use
=2^3
or
=POWER(2,3)

both will give you 8

Ofcourse you can use
=POWER(A1,B1)
with A1 and B1 having numbers...

Hopefully that is what you wanted... If not then my aplogies...

Let us know with an example.
 
Mark Anthony Browne -

If you are referring to the Power trendline, here is a relevant excerpt from
my book "Data Analysis Using Microsoft Excel":

"The power model creates a trendline using the equation

y = c * x^b.

Excel uses a log transformation of the original x and y data to determine
fitted values, so the values of both the dependent and explanatory variables
in your data set must be positive. If any y or x values are zero or
negative, the Power icon on the Add Trendline Type tab will be grayed out.
(As a workaround, you can add a constant to each y and x value.)

The power trendline feature does not find values of b and c that minimize
the sum of squared deviations between actual y and predicted y (= c * x^b).
Instead, Excel's method takes the logarithm of both sides of the power
formula, which then can be written as

Ln(y) = Ln(c) + b * Ln(x),

and uses standard linear regression with Ln(y) as the dependent variable and
Ln(x) as the explanatory variable. That is, Excel finds the intercept and
slope that minimize the sum of squared deviations between actual Ln(y) and
predicted Ln(y), using the formula

Ln(y) = Intercept + Slope * Ln(x).

Therefore, the Intercept value corresponds to Ln(c), and c in the power
formula is equal to Exp(Intercept). The Slope value corresponds to b in the
power formula."

- Mike

http://www.MikeMiddleton.com
 
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