# Test data for differences

I am trying to figure out the best way to test my data for differences in R. The data I have look like this:

domain               variable    lifecycle
162                      CSP1         5
162               old Species        10
162                        BD        16
162                       DBH        14
162                    Height        16
162                      Year         5
123                   species        12
123                  den bran        14
123                  den core        14
191                      CSP2         4
191                   C kg ha         5
185                  location         5
185                   biomass         6
82                   CSP num         6
82                  depth lb         8
82                       C t         7
190                     Layer         8
190                Dry weight         9
204                 item plot         5
204               item volume         7
204 within central plot small         7
205                      plot         3
205        successional stage         3
205            rarefy hundred         3


Now I want to use the "variable" column as factorial group and the "lifecycle" as the characteristiom to compare. Because the data is not normally distributed and I have more than two groups to compare I chose a Kruskal-Wallis test, which shows no significant differences.

Kruskal-Wallis rank sum test

data:  lifecycle by variable
Kruskal-Wallis chi-squared = 25, df = 25, p-value = 0.4624


My question is now if I can use the Kruskal-Wallis in this case to find differences in "lifecycle" for the "variable" groups, or is the sample size to small with only one value per group?

And if it is not usable here in this case what would be a better solution?

EDIT:

I did the Kruskal-Wallis now with the domain as grouping factor. Which gives me a significant difference. The interpretation would be that there are domains with significant more or less impact than other.

After that I performed a post-hoc test to see between which of the domains the differences occur. But supprisingly the paired wilcoxon test with bonferroni correction showed up no significant grup differences. How could this be?

• I think you have some big troubles on you data. What hypothesis are you trying to test?, what is your response variable? what does life cycle means? (I am a biologist but it is not clear in your data). You have many categories on the "variable" groups (some of them are non-sense), what about replicates?, as stated you have no replicates?. Please REVISE the WHOLE DESIGN of your study. It is not clear at all. – Damian Aug 13 '12 at 14:53
• This data is an analysis about a scientific workflow created with the workflow software Kepler. Could be that the name "lifecycle" is a bit missleading and to call it "Impact Factor" would be better I guess. The "Impact factor" describes a count of how much Influence a Variable has on other components of a scientific workflow. The hypothesis would be: There are variables with a significant higher impact factor than others in an scientific workflow. The response would be the count of workflow parts the variable affects. Best Sab – user13261 Aug 13 '12 at 15:22