This page is intended to provide information which may be useful for students enrolled in Statistics courses who are considering whether to purchase a scientific calculator or a graphics calculator.
Soon after the invigilator says “Stop work.” at the end of a Statistics exam, someone near you is bound to ask, “Did you finish?”
Whether you answer “yes” or “no” depends on a couple of factors including:
how well you learned the topics covered in the test; and
how quickly you were able to perform the various steps.
For all but the most trivial calculations, the TI-84 and TI-Nspire help you perform the steps more quickly than any scientific calculator. Even something as simple as calculating a mean (average) and standard deviation is faster because the TI calculators return both values on the same screen. Scientific calculators usually make you retrieve each value separately.
At the same time, the TI calculators will also return the minimum, median and maximum values on that very same screen. Most scientific calculators are unable to calculate the median, leaving you to do it by hand. The process is straightforward:
Sort the list of numbers into ascending order.
Calculate the index position of the middle value: ix=(n+1)÷2.
If the index position is a whole number, return the value at that index position.
If the index position is not a whole number, average the two values either side of the index position.
Sorting takes time and is tedious. Counting off index positions takes time and is tedious. Tedium is the ancestor of mistakes. It is much faster and more accurate just to press a button.
In essence, the TI calculators are optimised for Statistics. Once you become proficient, a TI calculator can easily save you up to 10 minutes per hour during exams. Think about it. That gives you up to an extra half an hour in a three-hour final exam.
You can devote that saved time to understanding the questions and double-checking your answers, all of which gives you the opportunity for higher marks.
Download the full story including hints on how to use TI calculators to solve typical problems you will encounter in statictics courses.
If a TI calculator seems expensive, consider the following:
It is going to help you pass this subject by saving you a lot of time in tests and the final exam.
You won’t have to remember anywhere near as many complement or approximation rules. The rules are easy enough but the complexities of having to perform multiple steps, each of which can involve applying multiple rules, and do it all reliably under exam conditions, can derail you — when the TI-84/TI-Nspire can do everything in a single calculation.
With the TI-84/TI-Nspire, you actually wind up having a better appreciation of how to approach and solve statistical problems because your mind isn’t cluttered with all the exception-handling. This is the difference between “teaching and learning” (aka “listen and regurgitate”), and “education” (aka “gaining true insight and knowledge”).
Although the TI-84/TI-Nspire excels as a calculator for Statistics, it has every function under the sun built in, so it will be useful for years to come. It’s also reasonably future-proof. Ask yourself how many other calculators come with a USB cable and software that:
If you are reading this early in the semester, it is unlikely that you will have a solid appreciation of the complexities of what you are about to face. Right now, the material seems simple and well within what you can handle with an ordinary calculator. You may not even have opened the Table Book yet. By the time you realise how much one of these graphics calculators can help you, it is almost too late to begin learning to use it because you are under far too much pressure (especially if you are a full-time student).
The price is also a lot less than the average smart phone.
Nothing is forever. You can purchase a TI calculator (either new or second-hand) and sell it again once you have finished your studies.
It’s your money and your decision. Just don’t blame me if you choose poorly.
Places to try (as of August 2013 — in alphabetical order):
Note: the above are neither recommendations for, nor endorsements of, any of the organisations mentioned.
You may well be able to get a new TI-84 or TI-Nspire at a better price elsewhere, so shop around. Keep in mind that many retailers will price-match if you ask, so if you do find a better price, take some evidence with you.
eBay is always a definite possibility. Quite a few students in past semesters have purchased either a new or second-hand TI calculator with the intention of selling it on eBay at the end of their studies.
CAS stands for Computer Algebra System. It means that the calculator performs the calculations symbolically. To understand what this means, consider a comparatively simple problem like 2÷3. From your high-school math class, you should know that the answer is, in words, one of the following:
Now, take those two different answers and multiply each by three. What you will do as a human is:
In essence, CAS calculators approach the problem by actually manipulating the fractions and employing simplification and cancellation rules. A CAS calculator sees the "divide by three" and the "multiply by three" and knows they cancel out.
While non-CAS calculators usually arrive at the same answer, they do it by using brute force (by maintaining a lot of decimal places of precision). Even so, they occasionally get it wrong. CAS calculators, on the other hand, maintain exact precision by using the rules of mathematics.
Because CAS calculators manipulate the mathematical symbols rather than just the numerical values, they can also perform other tricks such as automatically rewriting equations for you into simpler forms and solving for unknowns. This can be extremely handy, particularly if you are worried that your math might be a bit weak.
You betcha! Consider an equation like this:
z = (x − x̄) ÷ sx
Given x=1, x̄=3 and sx=1.6, you should be able to substitute the values into the equation and calculate that z=-1.25. But, what if you were given z, x̄ and sx and asked to calculate x? If you are thinking, “that is easy, I just rewrite the equation like this”:
x = z × sx + x̄
you would be absolutely right. On the other hand, if you thought that you should know how to rewrite the equation to solve for x but were not sure you could remember exactly how to go about it, or were not sure that you would always get the correct answer, then two things are true:
You are not alone. Probably 90% of your class this semester are in exactly the same boat. They are not sure of their math basics. They are not sure that they can remember the rules of algebra properly. They are worried about it.
Help is at hand because the TI-Nspire CX CAS understands algebra. It can do things like solve equations for you.
On the TI-Nspire CX CAS, you just use the original equation with the values you have (z=-1.25, x̄=3 and sx=1.6) plus the placeholder “x” for the unknown, and you tell the calcator to solve for x:
solve( (-1.25 = (x − 3) ÷ 1.6) ,x)
and, hey presto, the calculator does the algebra to rewrite the equation and solve for x. Magic. Kiss your math worries goodbye.
Choose the TI-Nspire CX CAS. There is simply no contest. The TI-Nspire CX CAS beats all other calculators hands down.
Do not make the mistake of choosing the “TI-Nspire CX”. You want the “TI-Nspire CX CAS”. Always look for the “CAS” suffix. Accept no substitues!
The TI-83 is just a TI-84 without a USB port. The programs written for the TI-84 will run on the TI-83 without modification. The problem is getting the programs onto the TI-83. You have three choices:
Enter the programs by hand. This is feasible but it will take you a fair amount of time and patience. It will also be up to you to ensure that you do not make any mistakes.
Find someone with a TI-84 to help you. You would have received a data cable with your TI-83 and that cable can be used to link a TI-83 to a TI-84. I believe the cable looks like the one shown in the (fairly poor) photo below. Assuming the programs have been installed on the TI-84, they can then be copied to the TI-83.
I believe it is now possible to purchase an adapter cable from Texas Instruments. The cable has a USB connector at one end, a clear capsule containing some electronics in the middle, and a plug for the TI-83 at the other end. I have never seen one of these cables but, in principle, it should make the TI-83 behave more like a TI-84 insofar as PC/Mac connectivity is concerned. You can find more information here.
The TI-89 is similar in appearance to the TI-83 and TI-84. I purchased a TI-89 with every intention of porting my programs to the model but I gradually formed the opinion that the TI-89 was not really optimised for the needs of students enrolled in Statistics courses.
I was not able to find an efficient mechanism for referencing lists. The TI-84 has keys for direct access to lists and the TI-Nspire presents the available lists in popup menus for easy point-and-click selection. The TI-89 appears to require multiple keystrokes. While one would become reasonably proficient with practice, given that lists are used so heavily in Statistics, I suspect the need to do battle with the calculator might get in the way of learning the subject matter.
I was also unable to find a mechanism to perform a linear regression where the result was returned in normal statistical format of ŷ=a+bx where a is the intercept and b the slope of the estimated linear relationship. The only option appears to be ŷ=ax+b which reverses the meaning of a and b. The need to perform mental translations for something so basic is, in my opinion, another thing that would get in the way of learning the subject matter.
One of the key reasons for preferring a calculator like the TI-84 or TI-Nspire over the combination of an ordinary scientific calculator plus table book is ease of access to distributions such as the Binomial, Poisson, Normal and student-T. In my opinion, getting to the relevant functions and statistical tests is harder on the TI-89 than either the TI-84 or TI-Nspire and, again, I found myself thinking that the TI-89 would probably represent an unnecessary additional barrier to effective learning.
Further experimentation may cause me to change my view but, for now, I am unable to recommend the TI-89.
A number of programs have been written to simplify some of the operations you need to perform. There are specific versions for TI-84 and TI-Nspire which you can download below. Unpack the .ZIP files then copy the programs onto your calculator via its USB cable.
The package for the TI-84 contains a number of separate programs which you install using TI Device Explorer, which is part of the TI Connect suite. The package for the TI-Nspire contains one document file which you install using TI-NspireLink. Both TI Device Explorer and TI-NspireLink are on the CD that came with your calculator.
If you have lost your CD or need an updated version, you can also find the software you will need at education.ti.com. Unfortunately, it can sometimes be a little difficult to find the connectivity software because it is not listed in a category of its own. You need to pretend that you need to update the operating system on your calculator, even if you do not need to. Links to the connectivity software can usually be found on the same page as the update.
These links may be useful. They were current as at August 11, 2013: