[R] Mann-Whitney U

[J Dougherty]

Natalie,

It's best to provide at least a sample of your data.  Your field names suggest 
that your data might be collected in units of mm^2 or some similar 
measurement of area.  Why do you want to use Mann-Whitney, which will rank 
your data and then use those ranks rather than your actual data?  Unless your 
sample is quite small, why not use a two sample t-test?  Also,are your 
samples paired?  If they aren't, did you use the "paired = FALSE" option?

JWDougherty