Re: Should I use rats or mice and how many?

Dear Jeff,

Research with rodents and mazes is typically done with both mice and rats, 
so either one will be fine.  (I personally prefer rats because they are 
not as smelly as mice, though mice are cheaper.)  Since you will be 
averaging maze completion times to compare the pre-trained rats to the 
novice rats, you should have as many as you can feasibly take care of.  
I'd say at least 5 in each group.  Otherwise, you may not get significant 
results between groups.  Make sure all the rodents you purchase are the 
same age.  When you order them from a science supply company (like 
Carolina Biological Supply), they will all have similar genetic 
characteristics and you can be assured they are the same age.  You need as 
much biological consistency as possible between your subjects.  So in 
other words, don't purchase them from your local pet store but order them 
from a science supply place.  You'll also want to keep them in identical 
environments, serve them identical food, etc.