# TI-83 Instructions

## Confidence Intervals for the Mean using a Large Sample

- Method 1 - Data
- Enter the sample data into a list, say
`L`_{1}

.
- 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`

, item #7. 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 (
`L`_{1}

) that contains the data.
- Press the down arrow twice, skipping 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 appears, in interval notation, along with the sample mean, sample standard deviation, and sample size.

- 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.