TLTR : New calculations suggest a light base set blister to be under 32.5g and heavy to be above 34.5g.
Quick Edit : Given@garyis2000 's post below, the lower boundary would drop to 32.3g. However, an heavy pack under 20.9g appears to be extremely unlikely, so a blister under 32.5g would remain extremely unlikely to contain an holo.
@sgbased : Thanks for sharing this. I edited the TLTR portion of my previous message. The data points you are providing are way off those I used in my calculations and I myself weighed a 1st edition blister today that was 0.4g outside my theoretical limit. It seems like pack weight (base set) is well confined between 20.5g to 21.42g with gray zone at 20.9g to 21.0g. It seems like blister weight (base set) varies between 32.1g to 34.92g. My goal was to try to estimate the average weight of the packaging and its error limits and add this to the pack weight gray zone boundaries to establish the blister weight gray zone.
Let’s try something different. I think we can establish the weight of the lightest and heaviest packaging (always based on available data). If we substract the weight of the heaviest pack to the weight of the heaviest blister, we obtain the weight of the heaviest packaging. Likewise for light. This is 34.92g - 21.42g = 13.5g for heavy and 32.1g - 20.5g = 11.6g for light. We can then add the weight of the lightest packaging to the weight of the lightest pack known to have an holo and add the weight of the heaviest packaging to the weight of the heaviest pack known to have an holo. We find 20.9g + 11.6g = 32.5g for the low boundary and 21.0g + 13.5g = 34.5g for the high boundary.
As mentioned, the weight will likely vary widely from one box to another and from one storage condition to another, but we have no reason to assume that the same holds true within a box or same environment. Unlike what I mentioned earlier (my mistake), the variance of blisters from a given box or provenance may actually be quite low. I would anecdotally report DFW.Pokemon saying that all their blisters (all with apparently the same provenance and storage condition) “weigh around 34g”.
The goal here is to establish boundaries where we can be almost certain that any given blister contains a holo or not, regardless of the storage condition or provenance. Given the data available, if my logic holds true, I believe that any blister under 32.5g has virtually no chance at a holo and anything over 34.5g is pretty much guaranteed to contain an holo. Probability of an holo will increase as the blister weight increases. On the low end, you have to hope that the packaging is light to allow a 20.9g or heavier pack. I don’t think we have enough data or can hope to have enough data to quantify this probability. In other words, I don’t think we can tell that a 33g blister, for instance, is unlikely to contain an holo. We would need to better know the distribution of blister weight (i.e. are low 32g blisters very rare? are high 34g blisters very rare?).
Makes sense?