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Show HN: Unsure Calculator – back-of-a-napkin probabilistic calculator

filiph.github.io

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Re: Show HN: Unsure Calculator – back-of-a-napkin probabilistic calculator

#141

Post by wongarsu »

spzzz wrote: post #130

This is really useful, but is this correct? persons = 10~15 // → 10~15 budget = persons * 1~2 // → 12~27 Should it not say 10-30?

If they are truly independent of each other some of the uncertainty cancels out. 10 people and a budget of $1/person are both unlikely events, and two unlikely events occurring independently of each other is even more unlikely. And because the calculator is not about the full range of possible values but about the values in the 95% confidence interval this leads to the outer edges of the range now falling outside the 95% confidence interval

Re: Show HN: Unsure Calculator – back-of-a-napkin probabilistic calculator

#142

Post by joshlemer »

NunoSempere wrote: post #58
NunoSempere wrote: post #41

I have written similar tools - for command line, fermi: https://git.nunosempere.com/NunoSempere/fermi - for android, a distribution calculator: https://f-droid.org/en/packages/com.nunosempere.distribution... People might also be interested in https://www.squiggle-language.com/ , which is a more complex version (or possibly https://git.nunosempere.com/personal/squiggle.c >, which is a faster but much more verbose vers…

Another tool in this spirit is https://carlo.app/ >, which allows you to do this kind of calculation on google sheets.

Their pricing is absolutely out of this world though. Their BASIC plan is $2990 USD per year, the pro plan is $9990/year. https://carlo.app/pricing

Re: Show HN: Unsure Calculator – back-of-a-napkin probabilistic calculator

#143

Post by duckmysick »

peeters wrote: post #139
Nevermark wrote: post #65

Earlier quoted context omitted.

From link: > Heaviest blue whale ever recorded I don't think estimation errors regarding things outside of someone's area of familiarity say much. You could ask a much "easier"" question from the same topic area and still get terrible answers: "What percentage of blue whales are blue?" Or just "Are blue whales blue?" Estimating something often encountered but uncounted seems like a better test. Like how many cars pas…

So the context of the quiz is software estimation, where I assume it's an intentional parable of estimating something you haven't seen before. It's trying to demonstrate that your "5-7 days" estimate probably represents far more certainty than you intended. For some of these, your answer could span orders of magnitude. E.g. my answer for the heaviest blue whale would probably be 5-500 tons because I don't have a good…

I don't know, an estimate spanning three orders of magnitude doesn't seem useful.

To continue your example of 5-7 days, it would turn into an estimate of 5-700 days. So somewhere between a week or two years. And fair enough, whatever you're estimating will land somewhere in between. But how do I proceed from there with actual planning or budget?

Re: Show HN: Unsure Calculator – back-of-a-napkin probabilistic calculator

#144

Post by JKCalhoun »

roughly wrote: post #44

I like this! In the grand HN tradition of being triggered by a word in the post and going off on a not-quite-but-basically-totally-tangential rant: There’s (at least) three areas here that are footguns with these kinds of calculations: 1) 95% is usually a lot wider than people think - people take 95% as “I’m pretty sure it’s this,” whereas it’s really closer to “it’d be really surprising if it were not this” - by and…

> 2) probability is rarely truly uncorrelated

Without having fully digested how the Unsure Calculator computes, it seems to me you could perhaps "weight" the ranges you pass to the calculator. Rather than a standard bell curve the Calculator could apply a more tightly focused — or perhaps skewed curve for that term.

If you think your salary will be in the range of 10 to 20, but more likely closer to 10 you could:

10or: 10!~20 (not to be confused with factorial)

or even: 10~12~20 to indicate a range of 10 to 20 ... leaning toward 12.

Re: Show HN: Unsure Calculator – back-of-a-napkin probabilistic calculator

#145

Post by gamerDude »

roughly wrote: post #44

I like this! In the grand HN tradition of being triggered by a word in the post and going off on a not-quite-but-basically-totally-tangential rant: There’s (at least) three areas here that are footguns with these kinds of calculations: 1) 95% is usually a lot wider than people think - people take 95% as “I’m pretty sure it’s this,” whereas it’s really closer to “it’d be really surprising if it were not this” - by and…

Great points. I think the idea of this calculator could just be simply extended to specific use cases to make the statistical calculation simple and take into account additional variables. Moving being one example.

Re: Show HN: Unsure Calculator – back-of-a-napkin probabilistic calculator

#146

Post by MichaelDickens »

Nevermark wrote: post #65
btilly wrote: post #52

Earlier quoted context omitted.

I strongly agree with this, and particularly point 1. If you ask people to provide estimated ranges for answers that they are 90% confident in, people on average produce roughly 30% confidence intervals instead. Over 90% of people don't even get to 70% confidence intervals. You can test yourself at https://blog.codinghorror.com/how-good-an-estimator-are-you/ .

From link: > Heaviest blue whale ever recorded I don't think estimation errors regarding things outside of someone's area of familiarity say much. You could ask a much "easier"" question from the same topic area and still get terrible answers: "What percentage of blue whales are blue?" Or just "Are blue whales blue?" Estimating something often encountered but uncounted seems like a better test. Like how many cars pas…

It shouldn't matter how familiar you are with the question. If you're pretty familiar, give a narrow 90% credence interval. If you're unfamiliar, give a wide interval.

Re: Show HN: Unsure Calculator – back-of-a-napkin probabilistic calculator

#147

Post by peeters »

duckmysick wrote: post #143
peeters wrote: post #139

Earlier quoted context omitted.

So the context of the quiz is software estimation, where I assume it's an intentional parable of estimating something you haven't seen before. It's trying to demonstrate that your "5-7 days" estimate probably represents far more certainty than you intended. For some of these, your answer could span orders of magnitude. E.g. my answer for the heaviest blue whale would probably be 5-500 tons because I don't have a good…

I don't know, an estimate spanning three orders of magnitude doesn't seem useful. To continue your example of 5-7 days, it would turn into an estimate of 5-700 days. So somewhere between a week or two years. And fair enough, whatever you're estimating will land somewhere in between. But how do I proceed from there with actual planning or budget?

I mean it's no less useful than a more precise, but less certain estimate. It means you either need to do some work to improve your certainty (e.g. in the case of this quiz, allow spending more than 10 minutes or allow research) or prepare for the possibility that it's 700 days.

Edit: And by the way given a large enough view, estimates like this can still be valuable, because when you add these estimates together the resulting probability distribution narrows considerably. e.g. at just 10 tasks of this size, you get a 95% CI of 245~460 per task. At 20, 225~430 per task.

Note that this is obviously reductive as there's no way an estimate of 5-700 would imply a normal distribution centred at 352.5, it would be more like a logarithmic distribution where the mean is around 10 days. And additionally, this treats each task as independent...i.e. one estimate being at the high end wouldn't mean another one would be as well.

Re: Show HN: Unsure Calculator – back-of-a-napkin probabilistic calculator

#148

Post by throwup238 »

duckmysick wrote: post #143
peeters wrote: post #139

Earlier quoted context omitted.

So the context of the quiz is software estimation, where I assume it's an intentional parable of estimating something you haven't seen before. It's trying to demonstrate that your "5-7 days" estimate probably represents far more certainty than you intended. For some of these, your answer could span orders of magnitude. E.g. my answer for the heaviest blue whale would probably be 5-500 tons because I don't have a good…

I don't know, an estimate spanning three orders of magnitude doesn't seem useful. To continue your example of 5-7 days, it would turn into an estimate of 5-700 days. So somewhere between a week or two years. And fair enough, whatever you're estimating will land somewhere in between. But how do I proceed from there with actual planning or budget?

> But how do I proceed from there with actual planning or budget?

You make up the number you wanted to hear in the first place that ostensibly works with the rest of the schedule. That’s why engineering estimates are so useless - it’s not that they’re inaccurate or unrealistic - it’s that if we insisted on giving them realistic estimates we’d get fired and replaced by someone else who is willing to appease management and just kick the can down the road a few more weeks.

Re: Show HN: Unsure Calculator – back-of-a-napkin probabilistic calculator

#149

Post by peeters »

Is there a way to do non-scalar multiplication? E.g if I want to say "what is the sum of three dice rolls" (ignoring the fact that that's not a normal distro) I want to do 1~6 * 3 = 1~6 + 1~6 + 1~6 = 6~15. But instead it does 1~6 * 3 = 3~18. It makes it really difficult to do something like "how long will it take to complete 1000 tasks that each take 10-100 days?"

Re: Show HN: Unsure Calculator – back-of-a-napkin probabilistic calculator

#150

Post by roughly »

jrowen wrote: post #76
roughly wrote: post #44

I like this! In the grand HN tradition of being triggered by a word in the post and going off on a not-quite-but-basically-totally-tangential rant: There’s (at least) three areas here that are footguns with these kinds of calculations: 1) 95% is usually a lot wider than people think - people take 95% as “I’m pretty sure it’s this,” whereas it’s really closer to “it’d be really surprising if it were not this” - by and…

This jives with my general reaction to the post, which was that the added complexity and difficulty of reasoning about the ranges actually made me feel less confident in the result of their example calculation. I liked the $50 result, you can tack on a plus or minus range but generally feel like you're about breakeven. On the other hand, "95% sure the real balance will fall into the -$60 to +$220 range" feels like it…

I think the point is to create uncertainty, though, or to at least capture it. You mention tacking a plus/minus range to $50, but my suspicion is that people's expected plus/minus would be narrower than the actual - I think the primary value of the example is that it makes it clear there's a very real possibility of the outcome being negative, which I don't think most people would acknowledge when they got the initial positive result. The increased uncertainty and the decreased confidence in the result is a feature, not a bug.
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