A coach claims a new training method reduces 5K times.
Using d = before - after, the appropriate alternative for "training reduces times" is:
- A
Ha: mu_d = 0
- B
Ha: mu_d != 0
- Ccheck_circle
Ha: mu_d > 0
- D
Ha: mu_d < 0
Explanation
If training reduces times, after < before, so before - after > 0; thus Ha: mu_d > 0.