Residual values in a spreadsheet

[DBeth]

I currently have my students working with residuals and making box
plots of them.

On the TI-83/84, one would enter their x and y values, compute their
regression equation, and then they could go back in their list and
enter a new list as RESID. From here, they could either do the
residual plot, or plot the residual values as a boxplot.

On the TI-nspire, getting the residual plot is TONS easier (just put
the regression line on the plot and then do the residual plot after
that). However, the only way I'm seeing to get the residual values in
a spreadsheet to make a boxplot of them is to compute the regression
equation on a calc page (menu, 6, 1, 3) and store the regression
equation to f1 (or whatever). Then, they can go back in the lists &
spreadsheet and create a new column with the rule y-f1(x).

I know a stat.resid variable gets created after computing the
regression equation, but the handheld won't let me enter that into the
lists & spreadsheet application. I can call it up on a calc page and
just see a list of values {0.45, -0.1, etc.}, but not in the lists.

Am I missing something easier, or does this seem to be the only way?
Thanks for your help.

[John Hanna]

2 suggestions to try:
In the name cell of an empty column in a SS, type stat.resid.
In the formula cell (the grey cell) type stat.resid. An '=' will appear
before it. Then name the column and use it in a box plot.

John Hanna
jeh...@optonline.net
www.johnhanna.us
T3 - Teachers Teaching with Technology
"A cowchip is paradise to a fly."

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[Dennis Williams]

I tried using the stat.resid in the SS and it gave me an error. I went
and took my stat.resid and stored that in a new variable and named it
residuals and then went to the SS in the name cell of a column pressed var
and Store Var and then var again and pasted in my new name residuals and
it gave me a list of residuals.

Hope that works and helps you.

Dennis

[Nelson Sousa]

Another option is defining a column as
b[]-f1(a[]),
where a[] is the column with your x-values, b[] is the column with the
y-values and f1 is the function where the reg equation is stored.

The advantage is that this definition is dynamical, whereas storing
stat.resid as a new list won't update automatically if the data
changes.

Yet another option would be defining a function:
define resid()=stat.resid

and recalling this function as your new column.

(By the way, I wasn't aware you couldn't use stat. variables on a L&S page).

Cheers,
Nelson

[DBeth]

Nelson,

Your first option is the way I've been dealing with it to this point.
In a way, it's nice because it helps refresh the true definition of a
residual, but at the same time, frustrating because of ridiculously
easy it is to make a residual plot.

I'll look into the variable redefinition and see how practical that
is, Dennis.

Thanks for the help everyone!

Damion