Tutoring math or statistics, you need to be familiar with various common scientific calculators. The math tutor continues the standard deviation series with a look at how to do it on Texas Instruments’ TI-30XA.

Unlike the Sharp EL-520W or the Casio fx-260Solar, the TI-30XA does not require you to be in a certain mode to use the statistical functions. Similar to the Casio, however, the TI-30XA is reverse entry. Therefore, to enter -18, you key in 18, then + ↔ –.

Example: Find the standard devation of the data set {-18,16,0,45,100,32,27}.

Solution: First, you should clear any data already in there. To do so, press 2nd 7. (If the stats memory is already clear, you’ll get Error. Don’t worry; just press ^ON⁄_C.) Notice the yellow CSR above the 7; I believe it stands for “Clear Stats Registers”.

Enter each number, pressing the Σ+ button after each. After you enter -18, then press Σ+, you should see “n=1” across the screen. Then, key in 16 and press Σ+, and so on. If you make a mistake, you can press^ON⁄_C, then enter the correct number and continue by pressing Σ+. If you want to remove an entry from the list later on, you can do so with 2nd Σ+. Noticing the yellow Σ- printed above the Σ+, you’ll get the idea.

Once you’ve entered the last number (in our case, 27), then pressed Σ+, it’s time to find the standard deviation. If you want σ_n, press 2nd ÷ (once again, see the yellow σ_xn above ÷). You should get 34.9, just like in the previous two articles. Otherwise, press 2nd √x to get σ_n-1. For Math Foundations 11, I believe σ_n is preferred.

Because the calculator I had in high school was similar to the TI-30XA, writing this article has been somewhat of a homecoming for me. I still appreciate the simple layout, with dedicated keys for square root and data entry.

Have a great weekend:)

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.