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exponential regression

  • To: mathgroup at smc.vnet.net
  • Subject: [mg129655] exponential regression
  • From: r.aufmann at gmail.com
  • Date: Sun, 3 Feb 2013 02:45:43 -0500 (EST)
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I entered Clear[a, b, x]; FindFit[{{1, 4.5}, {3, 14.0}, {5, 28.6}, {7, 54.1}, {8, 78.6}}, a*b^x, {a, b}, x] as a text of exponential regression.  The input returned {a->4.66625, b->1.42272}

Fine.  However, a student of mine entered the same data in a TI-84 calculator and it returned 3.947506 (x^1.334589).  These two equations are obviously not the same.  Does anyone know why there is a discrepancy?  By the way, I tested a data set that is exactly exponential. FindFit and the TI-84 returned exactly the same equation.

Thanks for any insight.



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