How to Use a TI-83 for Figuring out Confidence Intervals for The Population Mean (Known Standard Deviation)
The TI 83 graphing calculator can help you figure out just about every confidence interval problem you come across in elementary statistics. The only difference between having “Stats” (statistics such as mean, or standard deviation) or “Data” (the actual raw, data), is that you will have to enter the data into a list in order to perform the calculation. If you don’t know how to enter the data is entered into a list, you can find the information in this article on cumulative frequency tables.
Confidence intervals for the population mean
Sample problem: 40 items are sampled from a normally distributed population with a sample mean (x)of 22.1 and a population standard deviation(σ) of 12.8. Construct a 98% confidence interval for the true population mean.
Step 1: Press STAT, then right arrow over to “TESTS.” Press ENTER.
Step 2: Press 7 for “Z Interval.”
Step 3: Arrow over to “Stats” on the “Inpt” line and press ENTER to highlight and move to the next line, σ.
Step 4: Enter 1 2 . 8, then arrow down to x.
Step 5: Enter 2 2 . 1, then arrow down to “n.”
Step 6: Enter 4 0, then arrow down to “C-Level.”
Step 7: Enter . 9 8. Arrow down to “calculate” and then press ENTER. The calculator will give you the result of (17.392, 26.808) meaning that your 98% confidence interval is 17.392 to 26.808.