unequal samples

I conducted a sound propagation experiment in which 20 different recorded roar-barks (the long distance vocalization of maned wolves) were played back at different sites(x3), hours(x6: 17h,18h,23h,05h,06h,11h), and with different speaker position (x2: straight forward and inclined upward 45o)...

Hello: I've never posted here before; hopefully this query isn't redundant. (I have tried to look through previous posts for an answer!). My problem involves difference of means, unequal sample sizes, and nested groups. The basics: I want to know whether the difference between two means is...