I don't know bit or BLAST either. Below are places that may be able to help:
Have you tried: http://www.ncbi.nlm.nih.gov/blast/megablast.shtml
In general, you can supply:
"How do you compare BIT scores using blast?" to answers.com for other sites.
1. http://www.ncbi.nlm.nih.gov/Education/B ... sary2.html
has a BLAST glossary and links to a BLAST information guide, Query tutorial, a tutorial, a guide and a PSI-BLAST tutorial.
2. http://www.ornl.gov/sci/techresources/H ... last.shtml
- has a tutorial on sequence similarity searching using NCBI BLAST.
1. The exact wording of your input to answers.com, or any other search engine, may have a big impact on your result. So, some experimentation may be needed.
2. Beware of sites that are just trying to sell you something. In answers.com, these are supposed to be segregated under "Sponsored Links." But, they occasionally leak into "Web Results."
I realize your query has been on the board for several days, and your deadline is fast approaching. So please excuse if you already knew all the sites above.