I have a group (group2) that contains zero data, and I want to know whether it is considered normal or not normally distributed.
I used the SPSS software, and it showed this result.
I also tried R, and it showed this message: Error in Shapiro.test(group2) : all 'x' values are identical
If I want to compare the following groups:
Group 1: 0.7, 0.0, 0.3, 0.5, 0.0, 0.0, 0.4, 0.3, 0.4, 0.0, 0.0, 0.0, 0.0, 0.2
Group 2: 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0
Group 1 is not normally distributed according to the Shapiro Wilk test,
group 2 is the one with the undefined Shapiro test results
What test should I use to compare the following, mean, median, variance, and difference between groups? What should I answer if they ask me what distribution group 2 follows?
EDIT: Just for clarification, Samples in groups 1 and 2 were prepared in the same manner, and a specific material was added to group 2 and not added to group 1 ( this material resulted in zero values). So in order to evaluate the effect of the added material, I have to compare these groups. to prove the significant difference and the good effect of the added material.