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I have the following output from from R.

I know we can calculate predicted values using the predict() function.

How can we calculate the predicted value by hand if X=2 or 3?

I'm using the below formula but my answer differs from the output from the predict() function.

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JPGS
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  • Does this work correctly when you use a first or second order polynomial? – James Phillips Apr 20 '19 at 18:52
  • No, it still does not work. Based on my understanding, if X=2, calculation should be Y=67.7944+(16.9254 *2)+(-8.5843*2^2)+(-0.8990^3). In R, the predicted value is 59.66852 but when I calculate manually, I get 66.58 – JPGS Apr 21 '19 at 07:56
  • See https://stats.stackexchange.com/questions/31858/recovering-raw-coefficients-and-variances-from-orthogonal-polynomial-regression/249202#249202. – whuber Apr 23 '19 at 03:44

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