Graphing Calculator Help: Two-variable Analysis



#9

Hey there, I'm a homeschooled highschool student and all I have to work with is a Durabrand 828 Graphing Scientific Calculator. If you want to see what it looks like, here it is:

I'm taking Saxon Advanced Mathematics, and I'm currently learning how to perform two-variable analysis using a graphing calculator. my book is somewhat idiotic, because it automatically assumes i know how to use a graphing calculator... even though this would be the first lesson I've had involving one. Anyways, this is all my book says:


Quote:
Graphing calculators use the least squares algorithm to do linear regressions. All you have to do is enter the x data points in one list, enter the y data points in another list, and press the proper key. The TI-82 gives the following display for these data:

LineReg

y=ax+b

a=-.2075

b=25.64

r=-.7824726541


Ok, so anyways I understand... in my textbook it says the data points are: x= 82,87,97,107,107 and y= 9.5,5.5, 7.5, 1.5, 4.6
So I just need to "enter the x data points in one list, enter the data points in another list, and press the proper key" but what the heck is the "proper key"? I don't know, I'm very confused and they didn't give me hardly any info. I don't have a flashiest calculator anyways... but isn't there a way I can do this? Please help!

Edited: 23 Jan 2007, 2:51 p.m.


#10

Mike Sebastian's review of your calculator mentions that it does offer two-variable statistics, and this would mean that it does have the proper key, or at least the appropriate function.

The photograph isn't crisp enough for us to know where that key might be. And I hate to patronize you with the the dreaded call to RTFM, but have you looked there? Did the calc come with a manual, either paper or on CD?

I don't think it is idiotic at all for your book to assume that the reader is familiar with the correct use of his or her graphing calculator. It seems like the text wants to teach you the principles of the math, but leaves it to you, your teacher, and the specific calculator manual as to how to use your particular hardware.

I know that students don't always have a lot of money but if your text uses the TI82 you may want to look at spending a little more and getting one in that series. It is sacrilege to admit it here, but for some purposes I really like my TI83+, which you can find easily on eBay for at most $50 (and some would say that is too much). I haven't invested yet in the HP50G (well over $100 new, but worth it), but I have the 49G+, and it took me about a minute to solve the problem you pose, and most of that was just entering the data lists.

Les

#11

You need to use the mode key and get your calculator into the Stats mode and you will probably bring up another menu (2-Var stats) and then enter the data either one column at a time or enter them as an x-y pair. Your Mode key is green, but I cannot make out the number that puts you into the SD mode. Once there you will probably get a 1-Var or 2-Var choice and how you enter data is probably mentioned in your documentation. You might consider referencing a Casio or Ti manual if yours doesn't give detail as the calculator manufacture may have copied either of these two.

Most of us here are Hp calculator enthusiets and know very little about the calculator you are now using (I believe one member here purchased the calculator you now use, a Walmart special, I believe). The calculator should have come with some documentation (I suspect it is poor documentation, but for the money, you did get quite a bit of calculator!).

Actually, I would suggest buying a bit better off of ebay such as an older Hp38G (damn good Hp quality) or a bit more powerful (but less quality) Hp39G+ from ebay for a bit more than the calculator you are now attempting to use. These two calculators are Hp's close equvalent to the Ti-82/83/84 series calculators and are really cheap via ebay for next to new or new calculators (they are algebraic and therefore not sought after by collectors such as ourselves).


#12

If you do decide to replace the Durabrand it appears that Samsoncables.com offers a new 39G+ for $40.

http://www.samsoncables.com/catalog/prodDetail.cfm?Prod_ID=364&Sku=HP39GPLUS

I hope this helps and good luck!

Regards,

John

#13

Hi Amy,

Your calc looks like it is a clone of the Texet GR4F-X3 (which itself is largely based on the excellent Casio 602P). There is a PDF manual for the Texet available on-line here.

There is an example of how to do linear regression on page 67 of the PDF. Have a look and let us know if that solves your problem.

#14

The 828 is very similar to the old Casioo fx-7000G of the mid 1980s. It was the very first graphing calculator.

To do your problem go to page 23 of the manual. Try to do the sample problem and then your problem. If don't succeed, tell me.

You can contact me directlv if you wish

I don't think you need to buy another calculator yet.

I will run your problem on my 828 and post the answer tomorrow.


The worst thing about the 828 is the miniature manual. If you go to the site listed on the inside of the back cover you can get full size printout to your screen.

#15

I solved your problem on my 828 in about 70 seconds.

A = 25.64

B = -0.2075

r = -0.782472654

where A and B are reversed relative to your values. That is because the 828 uses the model

y = A + Bx

while the TI-82 uses the model

y = ax + b

The HP-42 uses the model y = B + Mx , That illustrates one of the things that you may want to consider if you decide to purchase a replacement for your 828. If the examples are done with the TI-82 then your tour through the course will go smoother if you select a machine with characteristics which mimic that machine;

A major advantage of using a TI machine is that TI has done much more work in the education market,


#16

Sorry to use the forum this way, guys. :-)


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