Consider the accompanying data on plant growth after the application of different types of growth hormone.
1. 13 17 7 14
2. 21 13 20 17
3. 18 15 20 17
4. 7 11 18 10
5. 6 11 15 8
a) Perform an F test at level \alpha=0.05
b) What happens when Tukey's procedure is applied?