Example: Estimating the average MLB Pitcher's age Section
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:
Descriptive Statistics
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.