In the early Pokemon card sets (base, jungle, fossil, etc), the weighability of individual booster packs was a well known QC problem. Since holofoil cards are heavier than regular cards (typically by several 0.1g), heavy packs typically had higher odds of containing such a coveted, typically more expensive shiny card. It was thus advantageous to keep such heavy booster packs sealed since they have increasing value over time.
In most recent sets, an extra, variable weight code card was added to each pack to counterbalance and randomize the weight of booster packs. However, social media rumor has it that the code card weight correcting scheme is broken and that Pokemon Scarlet/Violet products are weighable again. This is investigated in a total of 5 products — three Scarlet/Violet booster boxes containing 36 booster packs each and 2 booster bundles containing 6 booster packs each.
To weigh the packs, a KitchenTour Digital Kitchen Scale is used (https://www.amazon.com/dp/B07D7P7MJJ?psc=1&ref=ppx_yo2ov_dt_b_product_details) which has a measurement range of 0.05g-500g with a precision of 0.01g. Given that code cards and packs vary within the 0.1g digit, 0.01g is sufficient to capture most pack weight differences with sufficient precision. The scale was tested to ensure it did indeed have a precision variation only within +/- 0.01g, so all reported measurements have error bars only within that range.
The histograms below show the weight of individual booster packs in the products. At each weight bin, the hits as well as their rarities (shown as colored stars) are stacked. The legend for card rarities is shown below. Since each pack has at least a guaranteed rare (one black star), these are omitted from plotting and only rarities starting with Double Rare are shown.
In general, mean pack weight can vary across products since different products seemingly had differently weighted code cards. However, the heaviest packs (which are typically heavier by at least 0.1g from the average pack) often had significant enrichment of hits.
Booster Box #1:
(No histogram but 3/6 of the “heavy” packs weighing >= 22.9g had hits compared to the average pack 22.85g packs with a 1/6 hit rate)
Booster Box #2:
The two heaviest packs had guaranteed hits, with the heaviest pack having an Illustration Rare and a Double Rare.
Booster Box #3:
The four heaviest packs had hits with 1 double rare, two ultra rares, and 1 special illustration rare.
Booster Bundle #1:
The sole hit fell in the second heaviest pack (though not the heaviest).
Booster Bundle #2:
The sole hit fell within the heaviest pack.
Conclusion: The heaviest packs do seem to be enriched for hits, compared to the average packs. The top 2-4 packs in most of the products typically had guaranteed hits, compared to the average packs which had odds closer to 1/10 which is quite a significant deviation. The findings indicate that QC may indeed be broken in Scarlet/Violet and Pokemon booster packs are weighable again.
The raw data for booster pack weights is available at: https://docs.google.com/spreadsheets/d/1NO0jj-qVtVVQrRk5chfilF6HXNKhyUqAjfuJDsYRBLc/edit?usp=sharing