Friday, September 28, 2012

[GW2] Opening Bags: the Anti-Bot Code and MF

The Guild Wars 2 subreddit has been invaded by science, and I love it.

Recording the results of 500 rag salvages, Lord Signis found that salvaging items isn't affected by the anti-bot code. Marko did a similar setup, and found that salvaging isn't influenced by magic find.

This got me thinking: what about loot bags?

TL;DR: The loot obtained from opening bags isn't influenced by either magic find or the anti-bot farming code.

In order to obtain a desirable sample size, I grabbed 1000 Bags of Pinched Goods from the Trading Post.

Doing this has one significant drawback. I'm essentially assuming that loot is determined at the time I open the bag, not at the time the bag is generated. I'm really hopeful that ANet decided to save on storage space. [Further testing required... its something I'm working on.]

On the upside, It felt like Asuran Christmas. With fewer explosions.

  • The first set of 500 bags was opened with 0% MF after a day of opening no bags.
  • The second set of 500 bags was opened with 111% MF 24 hours later. (MF sources: 30 on jewelry, 53 on runes, 18 on gear, 10 from guild bonus)
  • I stood in the same place without moving on each run.
  • The bags were opened at 7pm EST 9/26 and 7pm EST 9/27.

Raw data can be accessed on this spreadsheet.

Each bag has a chance to contain a gathering tool (ex: axes, mining picks), a cooking item (butter, blueberries, blue meats), white crafting components (cloth/leather), or blue crafting components (claws, totems, etc).  In what follows, I'll break those categories down into gathering tools, white crafting materials, and blue crafting materials. I'll note whether the items are cooking components or not.

The Anti-bot Code.

The number of items contained within each bag does not decrease as more bags are opened.

For example, taking a look at the blue line in the center panel, across all 500 bags, if the bag contained butter, it averaged just under 4 butter.  This was as true for the first 100 bags as it was the last 500 bags. The order the bag was opened didn't change the amount of loot inside. [For the more stats-minded, the order the bags were opened was not statistically significant across several specifications of negative binomial regressions.]

The chance a bag contains a white vs blue item does not change as more bags are opened. Here, following Lord Signis, I'm taking a look at the change in the probability that an item contains a blue crafting material as the number of bags opens increases. While I had a run of good luck at the beginning, and a spot of rough luck around 250 bags, its fairly clear that the probability of a blue item hovers around 50%.

[Again for the more stats-minded, I confirmed this with a few specifications of probits of blue vs white on order with various controls.]

Based on the the first set of 500 bags, I didn't find any evidence that the anti-bot code changes the rewards from bag opening.

Magic find results. Here, I'm comparing the results of the first 500 bags (discussed above) to a second set of 500 bags I opened under identical conditions, 24 hours later, this time with 111% magic find.

Cooking Materials 0% Magic Find 111% Magic Find
Butter 317 324
Blue 16 18
White 24 23
Non-Cooking Materials 0% Magic Find 111% Magic Find
Blue 224 231
White 259 254

Not only is the difference between the two runs absurdly small, the difference isn't statistically significant. I only obtained seven additional non-crafting blues with 111% magic find - a 3% difference between the two samples, which is well within the margin of error (approximately +/- 4%).

Again, the punchline: the quality and amount of loot from bags isn't affected by either magic find or the anti-bot farming code.

Update: dev post - MF only works on kills.


  1. I really like these kinds of posts (even though I don't play some of these games). In fact, they are part of the reason I'm taking stats one through

    What tool do you use for your analysis and graphs? We are using R for the online class.

    1. Oh wow, that is excellent.

      For most of the stuff on this site, I used R with a mix of python/perl. For graphics, I use the ggplot2 package. You can find a great introduction at
      or take a look at Hadley Wickham's pages

    2. Oh cool, thanks. I will check that out. And just for reference sake, 20 years ago I graduated college with a degree in math and theoretical economics, so I had several stats classes back then. I just haven't used any of it since and have forgotten it all.

      I was reading this article yesterday, and now wonder if you are in this field or it interests you. Looks like it is a great time to enter the field!

    3. That is my field! And I love it. I get to work on all sorts of different projects, and pick just the right tool (program or method) on each.