Summer of Math Exposition

Presented by 3Blue1Brown 3blue1brown

The Most Controversial Puzzle in Probability

Audience:

Tags: conditional-probabilityprobabilitypuzzleparadox

The video unpack the famous “Two-Child Paradox” and how it managed to stump some of the most respected minds in mathematics.

Here’s the problem statement: I have two children. One of them is a boy born on a Tuesday. What is the probability that both children are boys?

This deceptively simple question hides one of the most controversial puzzles in all of probability. The answer seems clear—until you start asking how the information was obtained.



Analytics

7.73 Overall score*
4 Rank
39 Votes
30 Comments

Comments

7

Bit fast overall. Otherwise very good!

8.1

By far the best video on the topic I have ever seen. This “puzzle” has bothered me for years and the explanation of left-handed vs right-handed son finally made it sink in. Definitely will use that example when explaining this paradox to others.

Great intro/motivation Great clarity in animations Great novelty and memorability.

And another overlooked fact: great pacing!

8.5

Most intuitive explanation I’ve heard on this topic so far

8

Novelty/Memorability: At first i thought it was going to be just another of the same thing that there are 1 million vids on already, but the any probability between 1/3 and 1/2 made it feel like a very cool factoid, both novel and memorable

Clarity: probably as clear as it could have been. The only thing i could think would make it better is maybe somehow explicitly facilitate the mental translation between the physical experiment selection perspective and the area chart perspective for people like me who are kind of mentally lazy

Motivation: i think i am just naturally motivated by probability paradoxes like this

7.9

This video has shed light on a paradox that I’d been struggling to understand for some time.

8.5

The content is extremely well presented: The animation is clear and the dialogue is well-worded. In my experience, probability is often so intuitive to the teacher that it’s hard for them to teach, but this video demonstrates the teacher’s clear understanding. The only critique I have is that the video moved quickly and so might be difficult to follow by those unfamiliar with Probability Theory or those who are not native English speakers.

6.8

When people try to throw tricky probability puzzles at me, I like to remind them that statistics don’t account for human behaviour… maybe you have a son named Mark, and a daughter also named Mark, just because you thought it would be funny to confuse database admins…

4.7

The music is a little bit too loud, repetitive, and quite distracting I would say. Apart from that though it would be a very good video!! A standard video would have simply explained the paradox and be done with it, but you went much further and generalized the problem! Very well done!

7.5

The visuals of this video looked professionally done. The video began with a good hook, and didn’t dwell on calculations, instead focusing on the ideas behind how to calculate the probability. There were also many opportunities given for the audience to figure out an answer on their own, which is critical to learning. The script seemed very tight, and stayed focused the entire time. Overall, this video was very well done.

9

Your Video was really outstandingly good. Your pacing was perfect cause even though you talked very fast, as you have always animated every point you were talking about I never had any problems following you. Also your animations that only include very little Manim but a realy smooth custom style are (together with the simple music and everything else) very pleasing to watch. The only minor thing I noticed was that if someone who is not 100% familiar with the topic of (conditional) probability hears your wording “we can get rid of half of each of these boxes” at 3:50 might be a bit confusing and you could expand your reasoning a bit more with something like “We count this case as only 50 percent because it occurs only half the time/is only half as likely”. But appart from that: This Video definetly opened my eyes since I only knew Gardners original answer to the problem. Keep going like that!

8

Great video! In general, the explanation is extremely clear. It takes the viewer from thinking “There’s no way Tuesday has an effect” to “It’s obvious that Tuesday has an effect”, which is a big accomplishment and highly memorable.

The one point I’m confused about is that the video says that Gardner posed a basic probability question as a puzzle and then was wrong, and only then did it become interesting. That doesn’t make sense. Why would he pose a question he thought was boring?

I found the voiceover to be too fast to process information comfortably, so I suggest not editing so tightly.

But overall, fantastic video.

7

Good video! Maybe you can extend to sleeping beauty paradox

7.5

good presentation of interesting counterintuitive facts

6.8

I’m am not sure I agree with everything you said here, but non the less, splendid delivery and way to make you think about a problem. Some of the details could have been hashed out a bit more, also does this have any real world applications? Seems like it could be related to the gamblers fallacy or have implications in insurance.

5.1

Watching the whole video was like an instant to me, but a long instant due to the constant background music which I find annoying. Other than that, the visuals, explanations, topic and contents are quite interesting. Also, despite the voice is seemingly fast, the pace is reasonable.

6.8

Very nice animations and explanations!

My criticism is that it went a little too fast. I had to pause the video many times to think through what you said, because it’s just such an unintuitive topic. I think it would have been nice to spend some more time on the sloppy process of struggling with the problem, because when it goes by quickly, the audience might mistake the math for just intuition, after they’ve just been told that intuition can’t be trusted here.

9
  • Easily my favorite video I’ve peer reviewed this year. An absolute masterclass in efficiency of script along with crisp visuals - that grid of weekdays and the fraction that eventually derives 2p4p\frac{2-p}{4-p} was incredibly intuitive and really locked everything into place for me.
  • I particularly appreciated the inclusion of historical context of this problem, which fit seamlessly into your explanation of the math itself, without distracting from it. I remember reading about this problem in a collection of Gardner’s articles and was fascinated by it, and this video does a better job showcasing the ambiguity than the original correction by Gardner himself.
8

Upfront: I’ve seen both this problem and this explanation many times before. The explicit formula was new to me but not particularly surprising, so for the most part I felt like I was in comfortable territory. I have had issues with a lot of those explanations, and I think that this one avoids them.

In particular, drilling down on how the overlapping case (“both boys on Tuesday”) is the sole determiner of the final answer was great, and the intuition behind the non-equal probability case of handedness struck me as particularly effective.

One more substantial thing that was new to me was the history. I knew of the controversy surrounding the original puzzle but that was about it. A nice bit of color for the folks more familiar, thanks :)

My least favorite bit was the gag at 8:15. It’s a style of humor that I used to appreciate but have tried to phase out recently. It just has the potential to be needlessly alienating to the intended audience, who is likely struggling to understand what is (clearly) a very subtle and difficult probability paradox.

7.8

Overall: great video. The video poses an interesting question for motivation, though the problem and solution the video explores aren’t novel. The problem is memorable because of the way it contradicts intuition and is presented in an exceptionally clear manner. I also want to praise the incredible animations, voice acting, and editing that make the video smooth.

8.2

Very good explanation, especially given the short runtime

I like that it was explained several different ways since this is hard to make click and really seems unintuitive if not explained the right way

The history discussed in the beginning was really interesting and surprising, and made it clear that even the simplest version of the problem can be really unintuitive

Personally I had a hard time understanding the paradox coming in despite learning about it several times, and by the end of the video for the first time it actually clicked. the left/right hand maybe helped the most for me to understand

7.3

Although this video talks about at times a really confusing and counter-intuitive phenomenon in conditional probabilities, it navigates it perfectly by stating the problem in a simple question, presenting its’ history in a relevant way and making simple yet sound logical arguments. For me, it is the most clear (and surprisingly simple) explanation why this “paradox” happens and what is the solution to it. I also really appreciate the fact that the creator did not just end the video after explaining the paradox, but went back to the originally posed problem and showed that there is more hidden complexity in its formulation, and by using the logic developed earlier, solved the problem, later generalising the result. It is a perfect demonstration of theory and application.

I cannot say that the video is very novel - this topic (and, in general, nature of conditional probabilities and hidden ambiguity in conditions) are infamous for their counter-intuitivity, seemingly equally valid, yet vastly varying results, hence there are many videos discussing this paradox or its equivalents.

7.8

The topic was really interesting and you managed to added more variants to let the viewer understand better the concept. I also liked the animations and the humor you included in some parts. However, I felt like you talked a little bit too fast, so I felt like I was getting all the informations together without the time for processing them and I thus sometimes had to stop the video to think.

8.5

Excellent video, very well explained!

7.7

The topic is not particularly interesting for me, but the creator did such a good job presenting it, I really enjoyed it. Animations, the pace and the structure of how the topic is explained are all done very well.

9

Awesome video. Best explanation of this topic I’ve seen.

8.7

I actually saw this video already! I’ve been a YATAQi fan for a while now. I think this was really good. Near perfect score.

6.1

I think the presentation style was quite good and that it’s a simple presentation to demo how different conditions can lead to different probabilities based on distinguishing parts. I liked the part where it did mention if something is rare, it is much more likely to carry more information.

I think more time could have spent trying to explain the controversy as more of an ambient space measurement semantics. If we note the final condition here. If we mention that the condition of being born is C, that always has a probability of 1 occurring, and still resolves to 1 of them being a boy, and still does not resolve the questions here strongly when the statement should be what is the probability of the next child being a boy given a condition here.

5.5

Cool topic to make a video on. Great visuals and the pacing/structure of the video was engaging.

1.9

I do not consider this to be a real paradox. Although it is well presented, the mathematics is simply not interesting.

7.3

An excellent video on a tricky problem in probability. I had seen the problem before, but I liked the way you explained the different variants of the problem.