Tests and metrics might be page-specific. For instance, "How long did Experiment User stay on Page X vs. How long did Control User stay on Page X?" That wouldn't cause any difficulty, assuming at most one experiment per page.
Even if more than one experiment is running per page, or if metrics are more complex (e.g. "Does showing a more prominent image result in more repins of that image over the next seven days?") there are methods that can help isolate the effects of an individual experiment.
Comments
Not necessarily.
Tests and metrics might be page-specific. For instance, "How long did Experiment User stay on Page X vs. How long did Control User stay on Page X?" That wouldn't cause any difficulty, assuming at most one experiment per page.
Even if more than one experiment is running per page, or if metrics are more complex (e.g. "Does showing a more prominent image result in more repins of that image over the next seven days?") there are methods that can help isolate the effects of an individual experiment.