The scores on a (hypothetical) vocabulary test of a group of 20 year olds and a group of 60 year olds are shown below:
| 20 yr olds |
60 yr olds |
| 27 |
26 |
| 26 |
29 |
| 21 |
29 |
| 24 |
29 |
| 15 |
27 |
| 18 |
16 |
| 17 |
20 |
| 12 |
27 |
| 13 |
|
a. Test the mean difference for siginificance using the .05 level.
b. List the assumptions made in computing your answer.