# 8.2.2.2.1 - Example: Age of Pitchers (Summarized Data)

8.2.2.2.1 - Example: Age of Pitchers (Summarized Data)## Example: Estimating the average MLB Pitcher's age

In a sample of 30 current MLB pitchers, the mean age was 28 years with a standard deviation of 4.4 years. Construct a 95% confidence interval to estimate the mean age of all current MLB pitchers.

We know that n = 30, \(\bar{x}=28\), and s = 4.4.

To create a 95% confidence interval of mean age in Minitab:

- In Minitab, select
*Stat > Basic Statistics > 1-sample t* - In this case we have summarized data so select
*Summarized Data*from the dropdown - Enter 30 for the sample size, 28 for the sample mean and 4.4 for the standard deviation.
- Select
*Options* - The default
*Confidence level*is*95* - Click OK and OK

This should result in the following output:

N | Mean | StDev | SE Mean | 95% CI for \(\mu\) |
---|---|---|---|---|

30 | 28.000 | 4.400 | 0.803 | (26.357, 29.643) |

\(\mu\): *population mean of sample*

We are 95% confident that the population mean age is between 26.357 and 29.643 years.