TI89 stats oddity (corr)

05302015, 12:09 PM
Post: #1




TI89 stats oddity (corr)
I was messing around with some curve fitting on my 89 Titanium, since, while it would probably score dead last if we ranked calculators by usability * documentation quality / feature set, it's got a pretty decent stat package on board. (And it's actually not too shabby for programming, if you don't mind the horrible keyboard layout.)
If you run a linear regression, you get a value for corr. Nothing weird there. If you run a polynomial regression, you get R^2. But if you run one of the intrinsically linear regressions  LnReg, ExpEeg, and PowerReg, you get nothing indicating the quality of the fit. Is there a mathematical reason for that, or is it just some really specific manifestation of laziness? My TI86 and HP 48 both give correlation for those regression types, but nothing for polynomial (and the 48 just doesn't do polynomial period). The TI36X Pro gives r and r^2 for the main four models, and R^2 for polynomial. My Casio fx9860g Slim behaves similarly to the 36X Pro, and also reports MSe for a number of the models, which I'm not familiar with. 

05302015, 01:55 PM
Post: #2




RE: TI89 stats oddity (corr)
MSe is the Mean Squared Error, the average of the squared differences between predicted & actual values.
The 38G has a similar statistic, RELERR. 

05302015, 02:15 PM
Post: #3




RE: TI89 stats oddity (corr)
(05302015 01:55 PM)Gerald H Wrote: MSe is the Mean Squared Error, the average of the squared differences between predicted & actual values. Yeah, I dug through the Casio manual just a little while ago and found that. Along with tons of other formulas implemented in various functions within the machine. For as awful as it is to program a Casio (lists are essentially unworkable; doing ANYTHING to an empty list throws a dim error), it's got a great feature set, and rather good manual. Still not sure what's up with the inconsistent reporting of fit quality across TI machines. 

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