A survey of 25 randomly selected customers found the ages shown in years. The mean is 32.08 years and the standard deviation is 8.89 years.
| 43 |
29 |
31 |
37 |
49 |
| 15 |
32 |
40 |
20 |
30 |
| 23 |
21 |
42 |
26 |
39 |
| 36 |
31 |
43 |
26 |
35 |
| 29 |
31 |
16 |
42 |
36 |
A) Construct a 95% confidence interval for the mean age of all customers, assuming that assumptions and coditions for cofidence interval have been met. (What is the confidence interval)?
B) What is the margin of error?
C) How would the confidence interval change if you had assumed that the standard deviation was known to be 9.0 years? (Basically, what is the confidence interval using the given population standard deviation)?