Your sample size it way too small for the stats to be meaningful
Expected range: 36.2 (average of the clicks) P-value: 0.14
Typically you look for p-values of less than .05 to indicate statistical significance. So unfortunately this one test suggests the data falls within the range of normal (random) distribution.
So you are saying that if I had 10x the data, then the Saturday opening rate and the Sunday response rate could've been completely different?
Perhaps something was happening that Saturday, something that the post failed to take into account. Perhaps something happened during those weekdays, causing more engagement than normal.
Interestingly enough, nothing was happening on that Saturday. That I actually checked.
I obviously don't disagree that there's a lot of variables in play and some vary faster than others. What I meant by "10x" was that if the list were 20k subscribers instead of 2k for this particular experiment - what would've been the chance of the Saturday open rate jumping up.
It doesn't invalidate what you've found, but does mean you should now continue on with your experiment to increase the sample size - and help ensure your data wasn't impacted by something else - e.g. vacations / a conference that was attended by many of your subscribers / etc etc.
To answer your specific question, if you had 10x more data, your margin of error (with 95% confidence) would drop to 1.39%, so yes, you could reasonably get fairly different results.
I was disappointed to read that you skipped Thursday and Friday. In my domain, Mondays are the peak of activity, slowly sliding down to a bottom on Friday/Saturday. I would have liked to see your numbers for every day. Next time! (In that case, your MoE would have been 5.37%, btw.)
PS. I don't know why I picked (mod 5). Makes zero sense now.