# TI-83 Instructions

## Confidence Intervals for the Mean using a Large Sample

- Method 1 - Data
- Enter the sample data into a list, say L1.
- If the standard deviation of the population is unknown, then find the standard deviation of the sample. Record this number.
- Press STAT. The STAT menus appear and the EDIT menu title is highlighted.
- Select the TESTS menu title. The TESTS menu appears.
- Select ZInterval, the 7th item. A list of options appears.
- On the first line are two options: Data and Stats. Use the arrow keys to select Data.
- Press ENTER.
- Press the down arrow once.
- Enter the standard deviation of the population, if it is known. Otherwise, enter the standard deviation of the sample.
- Press the down arrow once.
- Enter the name of the list that contains the data.
- Press the down arrow twice (skip over the Freq option).
- Enter the confidence level as a decimal, not a percent.
- Press the down arrow once. The word Calculate begins to flash.
- Press ENTER. The confidence interval, in interval notation, along with the sample mean, sample standard deviation, and sample size, appears.

- Method 2 - Statistics
- Follow Steps 3 – 5 in Method 1 above.
- Use the arrow keys to select the Stats option.
- Press ENTER.
- Press the down arrow once.
- Enter the standard deviation of the population, if it is known. Otherwise, enter the standard deviation of the sample.
- Press the down arrow once.
- Enter the mean of the sample.
- Press the down arrow once.
- Enter the sample size.
- Press the down arrow once.
- Follow Steps 13 – 15 in Method 1 above. The confidence will appear along with the sample mean and the sample size.