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HP 48G Linear Regression Best Fit Line
12-21-2021, 12:59 AM
Post: #38
RE: HP 48G Linear Regression Best Fit Line
When I saw the results of MNH's office software:

Point: 248 Offset: 0.24655 Right
Point: 249 Offset: 0.24033 Right
Point: 251 Offset: 0.78342 Left
Point: 252 Offset: 0.06476 Right
Point: 254 Offset: 0.23177 Right

The words "Right" and "Left" led me to think that the offsets were taken in a direction parallel to the coordinate axes. I didn't notice the sentence just above that said "The orthogonal offsets to the BFL are". :-(

But it's easy to adjust the offsets to be orthogonal offsets with a few additions to OFIT. Here's the new OFIT:


With this version I get:

[ -.24655 ]
[ -.24033 ]
[ .78342 ]
[ -.06476 ]
[ -.23177 ]

Which is exactly what MNH's office software gets, evidence that orthogonal
offsets are what they want. :-)

The variance of these data is very small and because of this almost any method of regression gets results very close to any of the others.

The result for the slope returned by ORTH is .008321172, but calculating it with Mathematica and 50 digit precision gets .00832117201288.

Calculating this problem with the summary statistics derived by the HP48/49g+/50g is not the best way, but even so the result from the ORTH and OFIT routines is returning 8 accurate digits as determined by the Mathematica result.
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RE: HP 48G Linear Regression Best Fit Line - Rodger Rosenbaum - 12-21-2021 12:59 AM

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