Probability and Statistics > TI 83 > TI 83 Confidence Interval Population Mean

This article shows you the steps for TI 83 Confidence Interval (Population Mean).

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## Ti 83 Confidence Interval Population Mean: Overview

The **TI 83 graphing calculator** can help you figure out just about every **confidence interval problem** you come across in elementary statistics. The confidence interval is a range of data that you expect values to fall between. A simple example: you might expect your weekly paycheck to be between $500 and $600. 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.

## TI 83 Confidence Interval Population Mean: Steps

Watch the video or read the steps below:

## Confidence intervals for the population mean

**Sample problem:** 40 items are sampled from a normally distributed population with a sample mean x̄ 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.”

**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 12.8, then arrow down to x̄.

**Step 5**: Enter 22.1, then arrow down to “n.”

**Step 6**: Enter 40, then arrow down to “C-Level.”

**Step 7**: Enter .98. 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**. This is the same as:

17.392 > μ > 26.808

That’s how to make a TI 83 Confidence Interval Population Mean!

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Currently in statistics class we are working with z scores. My table only goes up to 3 or 3.5.I’m suppose to find the z score for the number 7 on my TI-83 but can’t find the info in the practically cheating handbook. Can you help? Thank you.

Brigette,

Any z-score greater than about 3.5 is going to have an are of about 4.9999.

For the TI-83, On the TI-83, the functions are

normalcdf(left,right,[mu,sigma]) finds the area under the normal curve (This function is listed under the “Distru” menu.)

Regards,

Stephanie

P.S. You can always check out our forums for any stats question :)

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