Question

Case study#1: The Wilcoxon-Mann-Whitney Test

Q. Soil respiration is a measure of microbial activity in soil, which affects plant growth. In one study, soil cores were taken from two locations in a forest: (1) under an opening in the forest canopy (the ‘gap’ location) and (2) at a nearby area under the heavy tree growth (the ‘growth’ location). The amount of carbon-di-oxide given off by each soil core was measured (in mol CO2/g soil/hr). Table below contains the data

Soil Respiration Data (in mol CO2/g soil/hr)
Growth				Gap
17	20	170	315	22	29	13	16
22	190	64		15	18	14	6

Perform Wilcoxon-Mann-Whitney Test and determine if there is significant difference between the two groups.

null hypothesis and the alternate hypothesis for each question.

Answer 1

For both question

Null hypothesis : Microbial distribution is same in gap location / growth location

Alternative hypothesis : Microbial distribution is not same or vary in gap location / growth location.