Tuesday, May 21, 2013

6-8 Weeks Later: Crit Success/Dice Rings Kickstarter review

I just got my rings from crit success in the mail.

If you haven't heard of them, the above video shows it pretty clearly.

There are various styles of rings, with multiple bands (for multiple simultaneous rolls), different "dice" (number of "faces", different icons, etc.) different colors, and, of course, different sizes.

The campaign itself ran pretty smoothly, and it ended up being around 2 months late- this would have aggravated some people, but I expect it with kickstarter now. Also, I expect that, if you're reading this, it's because you're interested in the product, since the kickstarter is long over.

I, my wife, and her brother all got rings, and all three were d20's (or, "r20's" as Crit Success has termed them), though of three different scales and with different finishes.

The advertised images were very good indicators of the final product. We got two smaller black rings, and one larger "rose gold" one, and the material was slightly lower contrast but better looking, actually. The difference was effectively just poor photography, I believe.

That's how I roll spin, or, how well do they actually work?

First, of the three rings, the rose and largest spun the best; the black and medium was okay, and we're going to try to get the smallest replaced, because it spins so poorly.

We washed them as instructed, twice, and eventually used everyone's favorite lubricant, WD-40, when that didn't help a lot.

When I was playing around with it, some numbers started appearing, so I tested my own ring, though from a smaller sample.

1 5
16 7
11 3
8 13
3 3
18 5
13 4
10 7
5 10
20 7
15 4
2 7
7 7
12 8
17 9
4 16
9 10
14 9
19 8
6 8

I somewhat arbitrarily stopped at 150, mostly because it was a round number and I was getting tired of this. Green indicates more than one above average, red is more than one below average, black is within one.

As a note, it took 81 spins to actually hit every number at least once.

I realize that the sample is small, but felt these numbers are pretty heavily skewed. Again, this was the ring of the three that spun the best. Also, out of a notably larger sample, it was noticing the prevalence of 5, 20, 17, and 4 when I had been playing around that had caused me to look into this.

As a note, I don't know if the variation in how well they spun was related to size, finish, or is simply bad luck and a correlation. If anyone else has experience (again, adding to the sample), please let me know.

ADDITION: I've added second and third sets of data at the bottom of the post.

The numbers are clearly skewed, which immediately kicks it out of the "wouldn't hesitate"list. Add to this the inconsistency in quality, and I'm a bit disappointed.

edit (yes, some more notes): I've been informed that these numbers are still around what's considered acceptable deviation. As noted in the comments below, my issue with it is that the numbers have stayed proportionally high and low, so I'm still skeptical. I'll continue recording data when I get the chance (see the bottom of this post for continuing data)

The materials are nice, and the ring looks pretty classy, though.

What it ends up being is a decent alternative when rolling dice, but I still expect to roll rather than spin when I'm not walking somewhere. Its material makes it better than a novelty toy, but the rather skewed probability keeps it off of the "must buy for any RPG-er" list.

If you're the sort that likes to casually play on the go, it's pretty fun. If you're looking for a thoroughly random device for gaming, I'm not sure I can recommend this.

edit: a question brought up on a forum:
"Did you randomise the start position of the ring ? or start it from a set point, or where it stopped last

it could be the bias you're seeing may be due to how hard you generally spin it

(the force you apply to spin the ring will be generally similar, so friction will naturally end up stopping in a similar position)

it's a potential inherent bias in the system"

When I was spinning it before testing, I wasn't starting in the same place; when I tested it, I always started at 1, and (as far as I could tell) got anywhere from around half a spin to two full spins out of each, so got some degree of variation.

In both cases, there were still the same notable spikes around or on specific numbers. I also tested it again after the recorded test, though I didn't record it: the same numbers still came up with regularity.

edit 2: the results:

NumberRandom start
(new sample)
Start on 1

This time it took 72 spins to get at least one hit on every number.

Again, it was a sample of 150

For the colors on the total, I'm doing within 2 of average (15) as black... I could have done one hit of variation, but the chart would have been nearly identical, except highlighting a few more lows and highs...

With the exception of 18, and 4, the greatest difference between the two samples is 3.

Added: rolling total (no pun intended). I don't know how frequently I'll be updating this, but I'd like to generate a larger sample over time...

last update: 5/25/13 (avg: 29.5)
1 29
16 20
11 25
8 43
3 24
18 25
13 26
10 34
5 34
20 35
15 20
2 30
7 37
12 33
17 30
4 37
9 34
14 29
19 22
6 29


  1. Even a perfect regular dice has a chance to roll n-times the same number. With that said, larger sample sizes tend to converge the actual and the expected result of infinite re-rolls. And looking at your most current data set the expected flat distribution around 29.5 \pm 5 seems to be a good approximation with most results within at most two \sqrt(29.5).

    Have you tried to repeat a similar experiment using regular dice? I bet their distribution will look quite like what you saw with the ring.

    Otherwise thanks for your thorough test and review (i found your blog while reading on dakkadakka btw).

    1. Hi, thanks for the input, definitely appreciate it, as I haven't done actual statistics since high school.

      There were definitely a few numbers that evened out over time, but my big concern is that the extremes have remained roughly proportional extremes... I don't know if that's something to be predicted, but it does seem like a pattern... again, it's been ages since statistics were part of my life in a meaningful way (i.e. beyond "this is around what's average on 3d6")

      Nope, haven't tried it with dice, though I guess it would be a lot faster... I may end up doing this as a comparison, but dunno how much more test rolling/spinning I have in me :P

  2. Have you washed the rings to get all the grit out? They spin a LOT smoother and longer when washed.