3 replies to this topic

[Crazierinzane]

Hello, I am a highschool student in an AP Statistics class, and I'm having an issue with my Casio FX-CG10 calculator statistics operations, specifically with finding residuals and doing regression tests.

So, the gist of it is, from testing between doing the work by hand, and doing it on the calculator, I'm getting incorrect results on the calculator (checked with my teacher.) I am also getting ridiculous answers, like getting more residuals than there are x and y values (or getting less, seems I get 8 either way for some reason.)

Example time:

I'm going to run a Regression tTest (TEST -> t -> REG) where Ho = 0 and Ha < 0
X list will be in List 1, the Y list will be in list 2, and goes as follows: n=19
|X| |Y|
2.5 211
3.9 167
2.9 131
2.4 191
2.9 220
0.8 297
9.1 71
2.7 172
0.8 211
0.7 300
7.9 107
1.8 167
1.9 266
0.8 227
6.5 86
1.6 207
5.8 115
1.3 285
1.2 199

After running the test, everything except the standard error is correct.
se = 37.8785798
Actual se = 3.457162419 (Formula used is (StdDev of residuals) / (StdDev of X multiplied by sqrt(n-1)

Now the residuals are really strange for me and my teacher. Assuming we have been talking about the residuals the entire time, the "Save Res: List" option, and I haven't completely missed something about statistics.
The residuals from the calculator regtTest go as follows:
-6.45
2.9e-6
17
260.56
-22.96
37.88
-0.84
0.7103

That's it. It only covers the first 8 values, and incorrectly as well. From what I know, there should be residual for all 19 x and y pairs, and they should add up to 0. This sums up to 285.88

The actual residuals are:
7.85
-3.98
-62.95
-14.43
26.04
etc till you have all 19

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I did discover one thin just now typing this up. I can get the actual residuals by going to the setup screen and having the calculator save all residuals from a regression test (and linear regression tTest) into a chosen list. This means I have to set the "save Reg: List" option to "none" so I don't get the wrong one.

Anyway, please tell me where I am wrong, thanks.


Edit: I did this with the calculator before and after updating the OS to the latest version, same results.

It's also very late at night when I am writing this, sorry if I made some unseen blunder.

I had something I felt like I wanted to edit into here, but I can't remember it now.

Edited by Crazierinzane, 02 May 2013 - 04:09 AM.

[Crazierinzane]

I guess I'm in the wrong forum.

That and I should have bought a TI.

[Castania]

If I'm going to work with the residuals, I always go to "Setup" from within the Stat Module and choose a list for them

"Resid List :List 8" or something . . . before I run the regression, test, etc.

I've never had the calculator fail to put the correct resids in place. Bear in mind, each time a regression is performed, the values in this pre-chosen list will be altered. So if you need to keep several lists of residuals, you'll need to copy from the chosen list to another open list. Hope this helps.

[Casimo]

See this topic: http://community.cas...tats-functions/
Isn't this a similar problem?