Archive for the 'Science' Category

Math questions

February 20th, 2005

A really amusing article about questions to ask after a complicated math lecture, to give the impression you can ask a serious question despite the fact that you really didn’t understand anything.

Surely a useful knowledge to have…

It’s relatively old (1983), but I think some of the questions are actually usable.  ;-)

Hat tip to Foreign Dispatches.

Suicide rates

February 14th, 2005

I noticed this lovely Guardian article talking about how according to WHO statistics "Europe is world’s suicide hotspot".

The article of course doesn’t mention Israel, so it wasn’t clear if we’re considered Europe or Asia for this purpose.
So off I went to the WHO website (They have a special, and large, suicide related area. How sad is that?), and looked at the statistics myself.

In the global comparison table, suicide rates here are higher than
some countries, but are indeed lower than the scary levels of most
west-European countries.

But it’s very hard to make anything from the data. What’s available
on the site is PDF files. The data is collected over different years,
and the PDF means it’s not easy to run any cross sections, sort the
data, or whatever… I certainly don’t care enough, or am bored enough, to
do hard manual work and check this for myself.

Personally, I’m not about the commit suicide in the foreseeable future, so there’s no urgency…

I am curious as to why suicide rates here are lower, though.
Sociological theories related to suicide (well, the few ones that I
actually came across. Really not my field, or area of interest) would
suggest this indicate people here are happier, or that the population
here is more cohesive. And I must say, they’re not, and it isn’t.
On the other hand, this is one mystery that I don’t feel any crucial imperative to explore…

Simple multiplication trick

February 3rd, 2005

Some education system teach children math skills by teaching them
how to do math. Some other education systems, ours included, starts by
forcing the kids to memorize lots of meaningless information that looks
like math, so that they will have the appearance of being able to do
basic math.

Such as the multiplication table. Instead of explaining to kids the
idea behind multiplying, they are forced to learn by rote the results
of multiplication of all pairs of single digit numbers.

I personally preferred to do the math. This meant that it usually took me a
bit longer than for some of my classmates to come up with the answer, but
it also meant I was never in a position where I couldn’t provide an
answer due to forgetting it…

In any case, here’s a simple trick that kids (can) use to aid in
this. It allows to get result for the whole multiplication table when
you only need to remember the lower half of it (1-5 times the rest):

Hold two fisted hands.

On each hand count off fingers by the
difference from the number and 5 (so it you multiply 6×7, count one
finger on one hand, and two fingers on the other).

Each finger that
you counted is worth 10 (in this example, that’s 2+1, so we have 30).

Now multiply the remaining fingers on each hand (4*3, after we used 1
and 2. So 12 here).

Add the two results. Presto! The
correct multiplication answer:
30+12 =42 = 7*6 .

Cute trick.

Of course, kids are mean towards anyone who is different, and so as
you may have noticed the trick only work if you have five fingers on
each hand. Those unfortunate souls scary freaks that have lost a finger, or the scary evil demon mutants with an extra finger, cannot use it as-is.

Gender Differences

January 19th, 2005

A Harvard Dr., in an informal speech, mentions that there may be innate differences <gasp> between men and women (link to NY Times article, registration required so I’ll quote heavily)
Naturally some women got offended, and demanded that he apologize.

The problem:

In citing a second factor, Dr. Summers cited research showing that
more high school boys than girls tend to score at very high and very
low levels on standardized math tests, and that it was important to
consider the possibility that such differences may stem from biological
differences between the sexes.

Or to present it plainly:

Dr. Freeman said, "Men are taller
than women, that comes from the biology, and Larry’s view was that
perhaps the dispersion in test scores could also come from the
biology."

The reaction, by someone who I’d have referred to as an hysterical women, except she’d take offense:

"When he started talking about innate differences in aptitude between
men and women, I just couldn’t breathe because this kind of bias makes
me physically ill," Dr. Hopkins said. "Let’s not forget that people
used to say that women couldn’t drive an automobile."

Yes,
let’s not forget that. Let’s also not forget the people that say that
men can’t get pregnant. Heck, let’s not forget those darn bigots that
talk about X and Y chromosomes as if there’s some difference in their
distribution between men and women. Or those people that say
chromosomes have any effect whatsoever on anything. A pity Dr. Hopkins
didn’t go into linguistics instead, I bet she could have made a
fascinating research about why most cultures develop different words
for "men" and "woman" as if they’re different in any way.

But maybe I’m wrong. Maybe this Dr. Summers is a known womanizer,
who always disparages women and think little of them. Maybe he didn’t
intend to raise any legitimate issues for consideration but just wanted
to insult women in general? Maybe not:

"A lot of people who absolutely disagreed with him were not irritated,
and he said again and again, ‘I’m here to provoke you,’ " said Richard
Freeman, an economics professor at Harvard who directs the bureau’s
labor studies program and invited Dr. Summers to speak. "He’s very good
at stimulating debate, but he cares deeply about increasing diversity
in the science and engineering workforces, especially since we have
many more women getting Ph.D.’s in science and engineering than ever
before."

Naturally, he didn’t apologize. There’s really nothing to apologize for:

The
president of Harvard University, Lawrence H. Summers, who offended some
women at an academic conference last week by suggesting that innate
differences in sex may explain why fewer women succeed in science and
math careers, stood by his comments yesterday but said he regretted if
they were misunderstood.

"I’m sorry for any misunderstanding but believe that raising questions,
discussing multiple factors that may explain a difficult problem, and
seeking to understand how they interrelate is vitally important," Dr.
Summers said in an interview.

People
need to calm down a bit, and not get offended when nobody tries to
offend them. People are different any any number of ways based on any
number of criteria. It’s possible to raise these issues in a derogatory
manner, but it’s also quite possible to discuss differences
scientifically and rationally.

Update: It reached our local newspapers this morning.
Unsurprisingly, they didn’t bother reading what they reported, and
instead went for the attention grabbing headlines. Translated: "Harvard Chief claims: ‘Women’s genes are inferior’ ". Which he of course didn’t.

A Very Bad Hair Day for North Korea

January 19th, 2005

North Korea is apparently a wonderful country in good condition. It’s after all a well known fact that you only get to deal with minor trivia once all the major problems are no longer pressing. So knowing that they have no pressing military, social or economic problems must be a comfort.

I mean, how else can you explain the fact that they have the time to worry about hair length?
Which should be shot. Sorry – a Freudian slip there, I meant short.

They even have a good reason for it, you see it just so happens that:

It stressed the "negative effects" of long hair on "human intelligence
development", noting that long hair "consumes a great deal of
nutrition" and could thus rob the brain of energy.
Men should get a haircut every 15 days, it recommended.

Yep. That’s what they say. If it weren’t a real country, and there weren’t real policies that affect real human lives based on this, I’d say it’s really really funny. As it happens, it’s just tragic.

  • Hair grows regardless of it’s length.
  • Hair doesn’t consume any nutritional resource by itself. Dead men tell no tales, and dead cells don’t eat. Hair is dead cells. Hair growth does take a small amount of nutrients, but hair grows regardless of it’s length.
  • Even if hair did consume lots and lots of nutrition – it still wouldn’t effect intelligence. Unless they’re claiming that this is what brings people to starvation. But if it causes starvation, long term effects on intelligence are the least of their concerns. Hair growth doesn’t barrow down into the brain to suck nutrients. Honest.

Now if you’d tell me that the persons that came up with this plan, and with these justifications, had really really long hair, I may be willing to reconsider. It still won’t prove a cause and effect relationship, but it would at least show strong correlation between hair length and negative effects on intelligence. That’s something…

Brain Scans Don’t Show Anything About Lies Or Truths

December 1st, 2004

Another case of wide publication for a juicy bit of news that  is based on rock-solid science. That is, assuming your definition of rock-solid is rather fluid.

The first news reports made this seem worse than it really is, I admit. It seemed so absurd that I just ignored it the first time I saw it. And the second time. And the… You get the drift. But it keep on coming, and most people seem to take this seriously for some reason.

Six people were asked to shoot toy guns, five people did not shoot the toy guns.
Then they were all placed under fMRI, and under polygraph tests, and told to alternately lie and tell the truth about the shooting.

And lo and behold, there were noticeable differences in brain activity.
Which led the researchers to assume lots of things about how the brain handles truths and lies differently. They want more funds to develop sophisticated lie-detectors based on this.

The original news reports (reporters must not be up to par these days) claimed that the shooters were told to lie, and the non-shooters to tell the truth, which of course turns the whole thing into a complete mess. The original news reports also claimed that there were six shooters and three non shooters, which strikes me as somewhat a lot harder for a reporter to miss.

One problem which is still there is the huge sample size. Eleven people. How do you get statistically significant results from that is beyond me.
Maybe they just need a baseline for these specific eleven people? This could work, get eleven suspected terrorists to do the research with you, ascertain that you know when they’re lying, and then interrogate them about their own terrorist activities… Somehow I have the feeling it’s not quite what they wanted here… Besides, if they were terrorists, they may have lied on the control questions as well.

Another problem is that… well… In this research both the fMRI and the polygraph showed distinct results.
But polygraphs pretty much suck at what they do. So now we know fMRI is as good as polygraph testing? Wow!

Besides, the polygraph testing itself was not even done with the best and newest polygraph techniques. Wrong type of control questions. The measured the wrong thing. They don’t have legitimate comparisons.
And when everybody knows it’s plain research and specifically told not to try and lie, and not to get excited, it can be expected that their brain activity (both for telling truth, and for lying) will be different from that of someone who is being accused of a serious crime.

Show me a larger sample, with cases where the polygraph fails miserably under best practices, and where the fMRI is accurate. Then there will be something worth considering.

Teenagers’ Behaviour And Health Survey

November 19th, 2004

There was recently a survey (Sorry, Hebrew link only) here in Israel assessing the behaviour and health of teenagers. One part, the one I found amusing, deals with safety and terrorism.

Apparently 22% of children from 6th to 10th grade feel, due to "political instability and the security conditions", that their lives are in danger. Riiight. Sure thing. Look around in a school, and every fifth kid feels their lives are in danger from terror. I’m convinced. Friends who have children at these ages just constantly talk about how their kids are terrified and all their kid’s friends are too. Not.

In addition, 37% of teenagers (Possibly out of the 22% above, the article phrasing is unclear) reported a terror event occurring next to their home, or knowing someone hurt from an act of terror. To which what I have to say can be nicely summed by WTF?! . Terror acts are great attention grabbers. People pay attention to headlines about terror more than to headlines about other things, like traffic accidents for example. But there just aren’t that many acts of terror. Not that many people die from terrorist activities. There are a lot more casualties from traffic accidents. The idea that 8.14% (0.22*0.37) of children personally know people hurt in acts of terror (How many friends away from home do kids have, for crying out loud?) is preposterous.
Unless of course the survey was not on a representative selection of the population, but rather focused in the more terror-stricken areas. But if that is case, which is contrary to what is stated in the article, then it has no bearing upon the general population and should not be used for anything in global political decision making processes.

Also, 34% of teenagers reported that the feelings of insecurity effect their social lives. Yea, right.
No less than 46% reports that it prevents them from going to "various places". Unless those places include the Gaza strip, this makes no sense whatsoever. Kids in these ages don’t make travel decisions apart from where do they want to hang out with friends. I can safely report from personal observation that the amount of people in general, and of teenagers in particular, did not noticeably drop from cinemas (About same amounts of screaming brats interfering with me watching a film in quiet), coffee shops, and the likes. Certainly not a drop as serious as 46%. Although to be honest, for those who are afraid to hang out with friends, 42% by the survey, this can certainly explain the change in social life.

And the cinch? 27% reported feeling less focused in their studies. Pe-leeeease. Schoolkids are not focused on studying due to worries about terror attacks? As if schoolkids need an excuse not to be focused in studying. How many of them bloody want to study at all to begin with?! Sounds like an excellent spoon-fed excuse.

Interviewer: "Do you feel that worries about terrorist activities causes you to be less able to concentrate on your homework and school material?"
Kid: "Less able to concentrate… on homework… eh… yes! Sure! Right! That’s it! I really do want to study hard! I do! But I’m so afraid some suicide bomber will come over to my house and explode while I’m at my desk! Yes! That’s why I don’t do my homework so well! Honest!"

Great survey. I hope nobody pays much attention. Don’t know how the other parts measure up, but if they’re up to the same exacting quality…

Wonderful scientific research

November 17th, 2004

This has to be about the most amusing thing I read in quite a while "Hours in front of a computer screen may increase the risk of
glaucoma in people who are myopic or near-sighted, Japanese scientists
said Tuesday
".

Glaucoma is high intra-ocular pressure (There are cases of "Normal Pressure Glaucoma", but since reducing the pressure even further helps in those cases, it says something…). It is not "caused by damage to the optic nerve" as stated in the article, it causes it.

It does cause visual field defects. The effects of the increased pressure starts to destroy nerve fibers from the outside in. Most people who do not go for regular medical examinations usually only notice they have Glaucoma after getting to a state of nearly tunnel-vision. The process is slow and gradual however, which is why it takes years for the effects to be noticeable.

For most people (without hereditary background), the time to start yearly checkups is at the age of 40 where it is most likely to start. The average age of people checked in this article is 43, and so without knowing the distribution there’s no way to know if the results are high or low. If they were all 43, the percentage of people with visual field problems with "suspected" glaucoma, about 1.66%, is not above the normal percentage in the population.
Now if the average age where 25 or 30, they would have had a strong case, as the percentage of glaucoma at these ages is very very small…

The whole "suspected" glaucoma thing is pretty suspicious as well. Checking intra-ocular pressure by an eye doctor takes about a minute, usually less. There are also simpler screening devices which are less accurate but can be used by anyone, and can get a pretty good idea if people have glaucoma or not. Unless they think all of the cases are caused by rare normal pressure glaucoma, of course… This would be harder to check, but is very unlikely and is not explained here…

So we have 5 percent of people with visual field problems, probably many of them above the age where these problems crop up anyway. About a third of these visual field problem may, or may not, be related to glaucoma (Which is considered the #1 reason for blindness overall, and so could likely account for more that 30% of all visual field problems even without any other factors included). If all of them are indeed suffering from glaucoma, the percentage is not different than for normal/random population at the relevant ages.

And not a word of explanation about the mechanism by which sitting in front of the computer increases intra-ocular pressure, or increases the susceptibility of the retina to be damaged from the pressure.

Oh, yes, and high myopia is a risk factor by itself due related condition of the retina (very roughly high myopia can indicate larger eyes, so the retina is more stretched to start with). If they get slightly above average percentage for people with high myopia (and the overall percentages here are at or below average), they don’t need the computer usage to explain it…

Yep. A lot to worry about. Now I have a good reason to stop spending all this time in front of the computer.

I just love it when science is done so well…

Hat tip to David Akin.

Encouraging Academic Excellence

November 16th, 2004

I have a friend who is studying for a Bachelor’s degree in Pol-Sci at TAU.

And one of their courses, passed by a lecturer who is not too good at teaching, introduces a new grading system. Nothing which isn’t widely used in some other types of degrees, but new for them. And the reactions of the students do not inspire too much confidence in the system.

This is from an IM chat with my friend, stripped of names and of interjected sentences that are not relevant to the subject, but not edited apart from that:

Yaron: How technical do they expect you to get?
Friend: very. Plus, since they are marking us on a curve as opposed to on the actual basis of merit, whoever gets the most intelligent person to do their homework for them gets the best mark!
Yaron: Youch!
Yaron: Don’t let the faculty dean or academic board catch you with that quote…

Friend: meaning???
Yaron: Grading on a curve is stupid. IMNSHO
Friend: yeah well, its their stupid system…. they have to take responsibility
Friend: and all people keep saying is:"I’m paying a PHD student to do mine, that way I definitely wont be in the bottom Part of the estimate…"
Yaron: That’s insane.
Friend: so….guess how much chance I have of getting a decent grade on my own…
Friend: but thats what happens when you add that element of competition to a bunch of deranged politics students
Yaron: Right. I forgot. PolSci. Where the subject material is used to bribe people…
Friend: see, i just figure its not fair if I try my best but get a 50 (or less) cause the rest of the class is paying a PHD student to do it for them. The exam is at least fair cause they cant cheat much on that
Yaron: If they know people are going THAT far out, they may decide to take the papers that don’t look like their students made, and disqualify them.
Yaron: It’s possible to differentiate between work made by BA students and work made by a PHD…

Friend: they wont. They cant prove it
Friend: plus, the lecturer would be flattered on his apparent teaching skills
Friend: This is why I hate political science this year…
Yaron: I can understand you, if this is the way things are going.
Yaron: Did I mention I think it’s insane?

Friend: I just dont feel confident in my ability to do a work that measures up to the "standard" if its going to be marked that way

We tried to figure out what may be good about the new system, but didn’t came up with much:

Yaron: There’s always the anonymous note option. Tell the lecturer, or someone higher up.
Friend: they dont care…
Friend: they just want money and jobs….
Friend: plus, the PHD students could do with the money at the moment….what with the taxes and all
Yaron: Trust you to find the moral justification. ;-)
Friend: ;)
Friend: its not their fault that people are taking advantage of the system!
Yaron: Maybe the university is doing it on purpose, as a community service.
Friend: exactly…

And in case it isn’t clear, a single student grumbling about paying someone to do a paper for them can usually be safely ignored, but when several start to exhibit this attitude it means they’re actually going to do it, and so are several more with enough intelligence to keep quiet about it.

That’s one way to show that even B.A. students serve mid-term papers at a level which wouldn’t shame a Ph.D. student elsewhere. It must be very impressive to show professors from other universities random sample papers from a B.A. class.

Oh, and just for the record, my friend did not pay anyone else to do the work. No one with, or studying for, a Ph.D. was involved.
I’ll know more about the actual grades in a couple of weeks.

too close to see

October 16th, 2004

This clinic, doing various eye surgeries for visual disturbances, have come up with a nice promotional material. They sent many ophthalmologists (Possibly other people as well, but I’ll stick to what I know) this small folded page to show clients/customers. On the outside a text instructs to Open the page, hold it in front of you with a stretched arm (about 40cm), and check your visual acuity. If you open the page, the inside have an almost standard visual acuity test page, with lines of text in decreasing sizes, each line marked by the visual acuity level matching the ability to see it clearly.

So far so good. You can look what is the smallest line you see clearly, and check if it’s the standard vision, or if you have a problem. And hopefully (from their POV), if you have a problem you’d notice their company logo and consider contacting them for treatment instead of buying glasses.

As a nice touch, it’s been the Jewish New Year recently, so the lines consist not of random numbers but of a text telling you to have a happy and successful (and so on and so forth) new year. Not good for a proper professional examination, but cute for this crude check.



If you go to an optometrist, or a doctor, to have your vision checked, you’d notice that there are two different checks. One is for distance vision, where you’ll usually sit in a chair a few meters from the test patterns you’ll need to try and read. The second is near vision, where you’d be given some card to hold in your hand at reading distance (about 20cm officially). The near vision of course you’ll only get if you’re over 40 years old, unless there’s a specific medical reason to consider a problem earlier. The important thing here is that there are two different systems, measuring two different problems. Well, not entirely separate of course, you’re using the same optical system after all. But the optical problems that glasses or laser surgeries address are commonly the result of different problems.

When looking to the distance (Infinity officially, but a couple of meters are close enough) you don’t focus your eyes, that is the lenses in the eyes are relaxed and stretched. The common optical problems are caused when light passing through the lens doesn’t focus on the retina, but either in front of it (Myopia – Nearsightedness. More common) or after it (Hypermetropia). This tend to change with age, since as you grow your eyes grow, resulting in light focusing in a larger distance from the front of the retina. That’s why usually glass numbers tend to grow, you need more correction to offset the distance. At about 24 years old, the body stops growing, and you no longer need to change your glasses.

Near vision, or reading, problems start at about the age of 40. In order to look at close objects the muscles around the lens need to push it. The closer the object, the more force needs to be applied in order to allow you to focus. With age the tissue of the lens becomes less flexible and it becomes harder to apply enough force. Then you need reading glasses to provide some of the optical correction. And unlike distance, using reading glasses increases the pace in which the problem grows, since the muscles become less exercised and weaken faster.

There are of course more problems, some also corrected by glasses, contact lenses, or these surgeries, but that’s not the issue here, so I won’t go into them.



Why the long explanations? To emphasize the point that checking near vision and checking distance vision are two different things.

And 40cm has a lot to do with near vision. Not entirely, that’s true, but enough. What you see from 40cm is not very relevant to your visual acuity for distance.

I tried to check myself with their test page. It was very interesting to see I get to 20/15. That’s wonderful! I didn’t see that well for more than 10 years… What an amazing improvement. Nowadays I’m actually more at the 20/20 or 20/30 range. Which is also good, but is normal good, not above normal good like 20/15 would be.



Which brings us to another alight problem with this test page, beside it being irrelevant and showing a clear lack of understanding about how visual acuity is checked (And I’m supposed to let these guys operate on my eyes after that?!). They had the Ft. scale and the 20/x scale. Would have been very nice for most Americans for example, that probably heard someplace you want to see 20/20. But around here the used system is 6/x mostly. Conversion is extremely trivial, but still it’s hard to believe someone around here would have come up with it. Which means they probably stole the idea from some American clinic doing the same thing…



These Y/X scales, if anyone wonders, are not at all complicated. The numbers say that what you see from Y meters an average person would see from X meters. So 20/20 means that you see from 20 meters what an average person would see from 20 meters. 20/40 would mean that what you see from 20 meters, an average person could see just as well from 40 meters. What matters is the ratio, so 20/20 is 6/6 is 5/5, and 20/40 is 6/12 is 5/10.

And these averages were measured a long while ago, and not extremely accurately. And they’re only averages, so seeing 6/7.5 (20/25) is perfectly fine and not reason to go buy glasses (or do some other things like this clinic sells).

Though IMNSHO the law here is a bit extreme, allowing people to drive if they see 6/12 in one eye. Putting a person with one blind eye (so having no stereoscopic vision, depth perception, at all), and another eye that needs to get to half the distance a normal person would in order to see a problem on the road, behind the wheel of a car, strikes me as not particularly safe. But maybe it’s just me, other people probably don’t need to see anything in order to drive safely.



Anyway, to get back on track, these people are using a scale which is rarely used in this country, and employ a meaningless method to do the check. And all that in a promotional material which is meant to attract customers who will pay them a lot of money to perform precise medical procedures on them.

I can’t see that happening.