## CSETMathGuru: THE Site for Single Subject Math

**What are the basic commands & functions on the TI 83 family of calculators for Subtest II?**

1. Since I use - and encourage use - of the TI 83 and 83+ calculators in my classroom, I am most familiar with the commands associated that model, and this article focuses on the same. However, click

__for a list of various commands and operations, and instructions to access them for the TI 81, 82, 83 and 85 models.__

**here**__is a "Quick and Dirty Guide" (!) for the TI-83 and 84 calculators;__

**This**__, too, is an excellent site packed with general operations.__

**this**The TI graphing calculators are 'forward' calculators in the sense that unlike more rudimentary apparatus like, say, the TI 30Xa, one types in commands and functions just as one writes it! In other words, punch in sin->36 instead of 36->sin.

2. To change modes: Degrees <-> Radians, use, er, what else (!) the MODE key, then highlight the required, er, mode!

3. Trigonometry commands are straightforward!

4. To get out of / cancel any operation:

CLEAR

or

2nd-> QUIT (which reposes above the MODE key on the TI 83+!)

5. Use ^ on the rightmost column for exponential operations ie. raising a number to a "power".

6. There is the Comma ',' key next to that of the round brackets '( )'. It's quite useful for advanced STAT commands.

7. This might appear a trifle inane but ALWAYS hit ENTER (bottom right corner) to execute a command.

8. To retype a command, there is the DEL key.

The key STAT functions and commands you might want to familiarize yourself with pertain to LIST operations.

1. To Enter/EDIT simple Univariate Data (ie. a list of X values ONLY):

STAT-> EDIT->Enter

Use Scroll (ie. arrow keys) to choose a List (L1, L2, etc.) and simply enter data.

Once done, 2nd-> QUIT shall you get you out.

(Do NOT hit CLEAR, which merely deletes what you typed last!!)

Keys you'll find frightfully useful to edit values:

DEL and CLEAR

2. To Enter/Edit Bivariate Data (ie. X and Y values, for a scatterplot, say) OR X-values with Frequencies:

As above, enter X data in L1, and the Y data / Frequencies in L2 (or whichever list you 'prefer' or is available for use).

3. For Univariate data expressed in Class Intervals with Frequencies - such Qs have appeared!! - enter the

*mid-values*of each Interval as X-values in L1, and the corresponding Frequencies in L2.

4. To find Mean (X-bar), Median (Q2 or 2nd Quartile or 50th percentile), Q1 (the 1st Quartile or the 25th percentile), Q3 (the 3rd Quartile or the 75th percentile), Standard Deviation (Sigma), for a Univariate dataset with Frequency = 1:

STAT-> CALC-> 1-VARSTATS->Enter -> L1 (the appropriate list!) ->Enter

Use ARROW keys to scroll down for Q1 (1st quartile), Q2 (2nd Quartile or median) and Q3 (3rd Quartile), Min and Max.

Remember: Variance is Sigma^2

5. To find Mean (X-bar), Median (Q2 or 2nd Quartile or 50th percentile), Q1 (the 1st Quartile or the 25th percentile), Q3 (the 3rd Quartile or the 75th percentile), Standard Deviation (Sigma), for a UNIVARIATE dataset with Frequencies in L2:

STAT-> CALC-> 1-VARSTATS->ENTER -> L1, L2 (lists separated by comma!) ->ENTER

Do NOT forget to use ARROW keys to scroll down for additional info like Q1 (1st quartile), Q2 (2nd Quartile or median) and Q3 (3rd Quartile), etc.

6. To find Correlation Coefficient, r, between 2 variables, as well as the Least Squares Regression Line: y = a + bx:

As before, enter X-data in L1, Y-data in L2. Then,

STAT-> CALC->OPTION 8 [Scroll Down and select or Hit '8'] LinReg -> ENTER -> L1, L2 -> Enter

This gives: r, r^2, a, b and y = a + bx where b ~ slope, a ~ y-intercept.

**In the event that you do NOT get 'r' or 'r^2' in the output**, turn DIAGNOSTICS ON thus:

2nd [yellow key on top left] ZERO (ie. CATALOG) -> Scroll Down to DIAGNOSTIC ON -> ENTER -> ENTER

7. For Bivariate dataset, to find X-bar, Y-bar, Sx, Sy, etc:

STAT-> CALC-> 2-VARSTATS->ENTER -> L1, L2 -> ENTER

8. To perform a Chi-Square Test of Significance, the formula is:

X^2 = Summation of [(O-E)^2/E]

with (r-1)*(c-1) degrees of freedom (d.f.),

where

O ~ Observed Value,

E ~ Expected Value under the Null Hypothesis,

r ~ # of Rows,

c ~ # of Columns.

This formula is rather cumbersome to perform by hand!

On the TI 8# machines:

a) Enter O values in L1, E values in L2.

b) Go to L3, and take the cursor up on top to Highlight L3.

c) Type in: (L1-L2)^2/L1, which of course, corresponds to the X^2 formula above!

d) To find the Sum of L3, you can simply use the 1-VARSTATS L3 command (explained above!) and note down the Summation-X value!

e) To find the P-value (am I making ANY sense here, or is this all gobbledegook?!!), use the command

2nd DISTR (it's above VARS!)-> Scroll Down to Option:7 X^2cdf -> ENTER -> (Summation L3 value, ######, d.f.)

where the 1st parameter is the Sum of the L3 values obtained in d) above; the 2nd parameter is a simply an ARBITRARILY large #; and the final parameter is the # of degrees of freedom using (r-1)*(c-1).

If this P-Value is > 5% => Reject the Null Hypothesis, Ho; if less, do NOT reject H0!

Finally, let me assert that by no means does one need to be absolutely wizardly with some of these 'advanced' calculator functions! One can quite competently compute many of standard numerical measures in Statistics slowly albeit tediously using 'regular' calculator procedures! The commands are, unquestionably, big time savers, and allows one to focus on the concept - What does this output mean? How does one interpret it? - rather than expend your resources on humdrum and wearisome calculations!

But if time is of the essence one might ponder acclimatizing oneself with the aforegone blather! Spend a couple of hours experimenting with the blasted thing, and one should be quite competent!