Mann-Whitney U-test

Problem 1

The growth form of young trees grown in pots can be scored on a scale from 1 (poor) to 10 (perfect). This score is a complex matter as it summarises the height, girth, and straightness of the tree. We have 15 trees. Of these, 8 trees were chosen at random to be grown in a new compost, whereas the remaining 7 were grown in a traditional compost. After 6 months' growth the scores were recorded:

Row	New Compost	Traditional Compost
1	9	5
2	8	6
3	6	4
4	8	6
5	7	5
6	6	7
7	8	6

1. State the hypotheses (H₀& H_a).

2. Perform Mann-Whitney U-test calculation in Minitab or SPSS.

3. Screen capture of the process and results in Minitab or SPSS.

4. Interpret results.

5. State the appropriate conclusion.

Problem 2

What is the idea behind this quote in relation to non-parametric test?

It is vain to do with more what can be done with less. William of Occam