Degrees of freedom in statistics (for t-test). I'm studying the sizes of bones which form in the eye of reptiles (scleral ossicles). I want to know if different "groups" of bones differ in size. I measured the size of each bone 12 timess - once in the left eye and once in the right eye of each embryo. When using stats should I use 12 df (because I made 12 measurements) or 6 df (because I used 6 different embryos)? Thanks!!!

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