The TI-89 graphing calculator can not only calculate z-scores and return values for normal distributions, it can graph the normal distribution curve as well. Graphing a normal distribution (a bell curve) can help you see what it is you are supposed to be looking for, and gives you one more tool in solving these types of problems. The TI-89 can graph a normal distribution with an area shaded for any value: less than a certain number, greater than a certain number, or in-between a certain set of numbers.
Sample problem: Draw a normal distribution curve for student’s salaries during a typical semester using a mean of $6,800 and standard deviation of $2,500. Shade the area that corresponds to salaries between $7,300 and $9,000.
Step 1: Press Apps and select the Stats/List Editor.
Step 2: Press F2 3 and F2 4.
Step 3: Press F5 › 1.
Step 4: Scroll down and enter 7300 in the lower value box.
Step 5: Scroll down and enter 9000 in the upper value box.
Step 6: Scroll down and enter 6800 in the μ box.
Step 7: Scroll down and enter 2500 in the σ box.
Step 8: Scroll down. Turn Auto Scale to “yes” by pressing the right scroll key, then the down scroll key to select yes. Press Enter.
Tip: If you want to enter ∞ (infinity) as one of your lower or upper values, press the ♦ then Catalog.