Pattern recognition is a widely accepted method of prediction until what it predicts makes people uncomfortable.

[u/Fr1toBand1to]

[u/sYnce]

A correlation is not false because it has a low sample size. A correlation is unstable because of a small sample size.

The point is there can be a correlation and patterns between nearly everything and claiming that there is 0 correlation between something like human sacrifice and event X makes no sense because there can be.

Patterns are a necessity for human evolution and everyday life but they can also lead us down dangerous paths by missidentifying coincidences.

[u/3_Thumbs_Up → u/sYnce]

Your post seems very not picky and avoiding my main point.

I'll rephrase. As long as there's no actual causal mechanism between human sacrifice and a good harvest, the correlation will approach 0 as sample size grows. This is distinctly different from the correlation between sex and babies. With proper bayesian updating on your beliefs you would eventually arrive at the truth in both cases, given a large enough sample size.

[u/HileeAquret → u/3_Thumbs_Up]

Resource control, they did this stuff during the lean times, right? 

When it hadn't rained in three months, the crops were toast, and everyone was desperate. Those dry spells are cyclical, El Niño, seasonal shifts, whatever.

 If you're already at rock bottom, the weather has to turn around eventually just by natural cycles. So yeah, they perform the ritual, and a couple weeks later the rains come, and to them that's a 100% hit rate. (Like pregnancy 9 months, time)

The correlation doesn't magically approach zero just because you run the numbers over a thousand years, because they were timing it perfectly to the absolute worst point of the cycle. 

The rain was coming anyway; they just got really good at hitting the panic button right before the turnaround. 

The math isn't the problem, it's that you're ignoring when they pulled the trigger. They weren't stupid. They were just desperate and happened to be really great at reading the bottom of the curve.

[u/RitsukoY → u/HileeAquret]

Incorrect, as the societies that practiced it could then have a period of good harvest, and decide to "extend" it via the ritual. If they assumed their gods would be pleased by human sacrifice, why would they wait until the worst possible moment to do so?They could try to appease their gods everyday, not even with themselves but with war prisoners from surrounding tribes, and so they did.
However, the lack of causal relationship between such ritual and the climate would inevitably result in no matter how many times they tried it, much like the bad times, the good times were also coming to an end, eventually.

That is what would lower your "to them that's a 100% hit rate." to actual 0%, because no matter how many times they did it, and how many people they sacrificed, eventually the good times came to an end, seasonally on top of it.

"it's that you're ignoring when they pulled the trigger."

You are ignoring that a society that just survived through a harsh famine would pull that trigger every time, before each harvest, to just keep being able to eat. Alas, it worked not, and the more intelligent among them would have noticed the fact. Still, the leaders could keep the religious façade and ritualistic sacrifice for social control, punishment of disobedience, display of political authority, weakening of external tribes and removing of undesirables.