How can I find out if the differences in length and width of cut marks left in fabric are significantly different between groups (knife types)?
KnifeType1 n=15 KnifeType2 n=15 KnifeType3 n=11 KnifeType4 n=15 KnifeType5 n=6 KnifeType6 n=4 KnifeType7 n=4 KnifeType8 n=5
I want to test length and width separately, and all measurements are in mm.
The data is not normally distributed, and the groups have very different variances; do I have to rely on Welch's t test?
I'm trying to determine if the lengths and widths of cut marks would help you determine what type of knife was used-possibly by seeing if the mean lengths and widths are sig different from each other. I'm using SPSS, and have a year of undergraduate stats.
Update I read that Welch's t test was pretty robust agains nonnormality, would it be okay to use that one and state that the normality assumption was violated?