How Well Do You Estimate? 374
A random UK blogger has published a quiz asking readers to estimate various numeric values which they may or may not have knowledge of; and has analyzed the resulting answers to determine how well people guess. The first part of the results looks at some specific questions, and the second part takes a look at the quiz overall.
Mythical Man Month (Score:3, Interesting)
Operational Research? (Score:4, Interesting)
Estimating distances.. (Score:5, Interesting)
If you have difficulty estimating a distance ( range), divide the distance in two, and try estimating that.
This sounds stupid, but actually works. Well, it worked for me. I'll never forget how I laughed in my head at the suggestion, and my astonishment at it actually working.
Mike.
Estimating Anecdote (Score:5, Interesting)
At lunches, we would sometimes try to stump our CTO a grey beard who is famous for work in information theory and general genius. We had never succeeded, even with obscure questions in biology "How do Prions work?", physics "What order are the colors of the rainbow, and why?", "How does the Corriolus effect work?", etc. that none of us had any particular knowledge of, and always had to research afterwards to determine the correctness of his answers.
So, I posed the question to the group "How many leaves are on that tree outside the window?" It was a ~30 foot tall, bushy tree in the height of summer. I hoped he'd take the bait.. I thought this was going to be very hard to "get right", and it would even be difficult come up with a plausible answer.
After a few moments, I set off the responses by saying that I thought it easily had 10k leaves, possibly 20k or more.
Everyone gasped. "Oh no! No way..." and then proceeded to offer lower and lower estimates.
The responses started with me and made their way up in the seniority ranks (I was the most junior) all the way up to the CTO. He said "Oh! those kinds of things are notoriously hard to estimate. We typically overestimate grossly in counting things of plentitude. Oh, I don't know. 200?".
Finally we had him. There was no way there were 200 leaves on that tree.
Later, in discussion, a trend became clear. The more senior the person, the more conservative was their response, even to the ridiculous level of our CTO saying a tree in full flush, that he could see right outside of the window, had 200 leaves, when it most plainly had many, many more.
Anyone want to hazard a guess? How many leaves on say, an adult Sycamore (or Maple, Oak, etc.)?
Time and Miles (Score:4, Interesting)
Similarly, I will look at the odometer in my car, drive a distance, and guess that it's 10 miles later. Looking down, 10.1.
The best is when you combine them. "How long before we get there?" the wife asks. "About 47 minutes," say I, and 47 minutes later arrive at our destination.
I note this only because most everyone else seems incredibly bad at this. As when someone gives you loose directions to a place like this, "Oh, go about 3 miles, then turn left on Main St." Half a mile later I'm slamming on the breaks 'cause I just past a sign saying "Main St." Or when they tell you it's a 5 minute drive, when it's really 15. Drives me batty.
In short, I estimate that just about everyone sucks at estimating. Funny thing is people always over-estimate distance and under-estimate time.
Re:I estimate (Score:5, Interesting)
Substitute +2 and 0 for low karma posters, obviously...
Looking back on my posts, I have shedloads of +5s and occasional -1s in a long list of +2s... but very few +3s. Moderation is a runaway process, in which the difference between +5 and -1 is a single modpoint.
sheds some new light on the DARPA terror pool (Score:2, Interesting)
When Poindexter tried to set up a terror gambling pool to predict terror events, he was relying on something like this-- that collective knowledge would somehow converge on the right answer, or something close enough to be useful.
The results from this survey suggest that that's probably true for something where the guessers/bettors actually have some real knowledge, however deeply buried in their memories it might be, but in areas where people have no information (the GDP), or worse, have been hearing sensationalized opinions (average amount that people get on the dole), they can be not only wildly wrong, but have no idea how wildly wrong they can be.
The terror pool gave me the impression that it was going to collect and integrate the wild ass guesses of its members to somehow develop predictions, but it wasn't clear that anybody would have anything better than WAGs, making it possibly of negative value, rather than providing the collected wisdom that was intended.
A sort of trivial example is if I ask a bunch of people to guess the number of jellybeans in a jar. If I show them the jar, the mean guess will probably be pretty close to the true value. In this case, each person is making an estimate based on seeing the beans and the jar.
If I don't show them the jar, or tell them anything about it, they can only make wild guesses, and I could have a tiny jar with a single jellybean, or a jar the size of the Rose Bowl with however many jellybeans that holds. In this case they're making guesses rather than estimates, and the statistics won't tell you anything about the number of beans in the jar (but may tell you something about how the guessers think of jellybeans and jars).
About the article... (Score:5, Interesting)
Reminds me of how they teach math now (Score:5, Interesting)
They spend a lot of time on grouping. For example What is 97 + 198? I was taught to add 8 and 7, carry the one etc...
They are taught to group the numbers, the instantly recognize that the answer is close to 300, then see how it differs from the 100s. 97 is 3 less, 198 is 2 less. Now add the 3 and 2, getting 5.
The answer is of course 300 - 5, or 295.
I find this method very intuitive.
Re:I estimate that... (Score:5, Interesting)
You must not be an American then
Take for example graduating from college. Did you know that there are no "below average" college graduates? Proof: In order to graduate from college you must have a GPA equating to a C or better. A C is average, therefore there are no below average college graduates.
Other estimates that I ask people from time to time. What percentage of the US population is African American (black)? What percentage of the US population has a college degree?
Although the African American question is a little skewed because of the area I live in does in fact have about 30-40% of the population as being black, the national average in 2002 is 13%. I typically get answers that the national average is 30-40%.
The college degree question is also very off. I typically get answers around 50% or higher, where its 27% as of 2003. Its some kind of myth here in the US that everyone has to go to college so they can do unskilled labor the rest of their lives. In fact, my aunt was lecturing her (adult) son that got his girlfriend pregnant with the "How are you going to pay for the kid to go to college?" routine. When neither of her parents went to college, neither her nor her husband went to college, and none of her 2 children went to college.
Ask an American and a Japanese if they are "good in math". The Japanese will typically say "no", the American will say "yes". Ask the same 2 kids to take a standardized math test, the Japanese will score better than the American.
However, although its important to feel good, its more important to look good!
significance (Score:5, Interesting)
Re:I estimate that... (Score:1, Interesting)
Statistically speaking, there will always be a portion of the population that is above average, and a portion that is below average. Regardless of what a school system may consider "Average" (C isn't really average anymore by the way, it's more like an "eh..at least I don't have to take it again next semester!").
In fact, at my old high school, a D was considered failing, however, in college, a D is passing (depending on the class taken..underwater basket weaving anyone?).
If the average graduate of a school has a 3.5 gpa, everyone blow that is below average, everyone above is above average.
Perspective (Score:3, Interesting)
You would be describing the difference between localized perception and overall truth, the essential gap between concept and reality.
For example, I can look at the North American business market and go "Wow! Microsoft owns this market!" because all I see is Windows on the desktops.
But in truth, it is the back-end data servers from a myriad of companies and providers which are entrusted with the critical business information, not the desktop. The desktop is merely an access point and a collection of utilities to help people analyse and format that information.
Re:Operational Research? (Score:2, Interesting)
(define (sqr n c)
(define (s x n c)
(if (zero? c)
x
(s (/ (+ x (/ n x)) 2) n (- c 1))))
(s n n c))
Construction estimation method (Score:1, Interesting)
Take your best guess, double it and move up to the next time unit.
So, a 1 week job becomes a 2 month one.
So far I'm 1.75 years into a remodel that I thought would take 6 months -- I hope to god it doesn't take 12 years, but it is starting to feel like it.
Interesting Idea For a Survey (Score:1, Interesting)
You are required to make a guess and give a plus or minus value.
For many questions, people may be 40% sure that the answer is either 9, 10 or 11, but there is a thirty percent chance that the answer is 5-8. Maybe the person percieves a 1% chance that the answer is 12 or higher and a 29 percent chance that it is 0-4.
The person taking the test would likely instinctively guess 10 as their answer, but then realise that +- 5 contains the range 5-15. Then they say: hmm. What number is in the middle of the range that has a 70% probability of being correct, that is 5-11? 8. So the answer is 8 +- 3. But most people would put down 10 +- 5 just because they didn't want to do the math to figure out how to enter their guess into the survey, and get a score lower than their estimation.
It would be easier for test takers to provide a range with a max and a min, and no guess. that way they don't have to do math to figure out what their optimal guess should be.
However, you could have someone who is 100% sure the answer is either exactly 12, exactly 120 or exactly 1200. Their optimal guess would be ( 12 + 1200-12/2 ) +- 1200-12/2. However, they know the answer is certainly not 13. Letting a person specify multiple ranges whose probabilities of being correct sum to 70% seems to make sence. Then someone can say: It's either 100-105 or it's 3000-3100, But it's not 106-2999.
There also needs to be a "I have no idea whatsoever". It shouldn't decrease a person't score. For instance, I had no idea what an MP was in the House of Commons. Likewise exact answers should be discounted from test results - there is no estimation going on then. Don't tell the test takers that being exact will lower their score though. Then they'd just put down a very restrictive range.
Re:I estimate that... (Score:4, Interesting)
This is not specific to the US. In Russia most people overestimate the percentage of people with higher education as well. (Don't have the reference handy, but you probably can't read in Russian anyway - but it's on fom.ru). Also, about 60% of Russians said they want their kids to become scientists - even while the average salary in science is around povery line and everyone knows it.
There are a lot of stereotypes regarding science, scientists and education, but we must be thankful, because they are mostly positive.
People are optimists and it shows. In fact, it is known in sociology that in many surveys (especially those about the future) people first make up their mind on whether they are optimistic or pessimistic and then answer based on this, regardless of the particular question.
Anchoring and adjustment (Score:3, Interesting)
Re:I estimate that... (Score:1, Interesting)
=====
1)admit anyone who applies to your school (with financial aid)
2)make sure they all get at least the minimum GPA to keep that scholarship/grant money flowing
3)PROFIT!