Two-cavity mold t-test

[EcoMan]

Hello,
I would like to test for a difference between a single lot of injection molded parts from each cavity of a symmetric two-cavity mold. I'm not sure whether to use a two-sample t-test or a paired t-test. Which test is appropriate for this case? I assume that the answer doesn't change if there are multiple lots produced under the same processing conditions.

 

[EcoMan]

Just to clarify, I'm interested in whether the parts are affected by which cavity that they come from. Assume balanced mold filling.