## 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 , then right arrow over to “TESTS.” Press .

Step 2: Press for “Z Interval.”

Step 3: Arrow over to “Stats” on the “Inpt” line and press to highlight and move to the next line, σ.

Step 4: Enter , then arrow down to x.

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

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

Step 7: Enter . Arrow down to “calculate” and then press . The calculator will give you the result of (17.392, 26.808) meaning that your 98% confidence interval is 17.392 to 26.808.

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## 3 Responses to “How to Use a TI-83 for Figuring out Confidence Intervals for The Population Mean (Known Standard Deviation)”

Oct 14, 12 at 6:30 pm

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.

2. ### Andale said:

Oct 15, 12 at 11:43 am

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 :)
http://www.statisticshowto.com/forums/

3. ### Using the TI-83 Calculator for Statistics | said:

Mar 05, 13 at 7:40 am

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