# Calculate a T-Interval for a Population Mean

Calculate a T-Interval for a Population Mean##
Minitab^{®}

## Procedure

A *t*-interval for a population mean provides an interval of estimates of the unknown population mean μ.

- Select
**Stat**>**Basic Statistics**>**1 Sample t**... - Use the pull-down options to select, '
**Samples in columns**.' - Select the variable you want to analyze, (by double-clicking, or highlighting and clicking once on '
**Select**'.) so it appears in the box labeled '**Variables**'. - Select '
**Options**' ... Type in the desired confidence level the default is 95.0 in the box labeled '**Confidence level**'. (Ignore the box labeled '**Alternative**'.) - Select
**OK**. - Select
**OK**. The output will appear in the session window.

## Example

The US National Research Council currently recommends that females between the ages of 11 and 50 intake 15 milligrams of iron daily. The iron intakes of a random sample of 25 such American females are found in the dataset irondef.txt. With 95% confidence, what is the mean iron intake of all American females?

## Minitab Dialog Boxes

## Sample Minitab Output

### One-Sample T: iron

Variable | N | Mean | StDev | SE Mean | 95% CI |
---|---|---|---|---|---|

iron | 25 | 14.300 | 2.367 | 0.473 | (13.323, 15.277) |