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Comment: p-value research is misleading almost always (Score 5, Interesting) 184

by SteveWoz (#49495363) Attached to: Social Science Journal 'Bans' Use of p-values

I studied and tutored experimental design and this use of inferential statistics. I even came up with a formula for 1/5 the calculator keystrokes when learning to calculate the p-value manually. Take the standard deviation and mean for each group, then calculate the standard deviation of these means (how different the groups are) divided by the mean of these standard deviations (how wide the groups of data are) and multiply by the square root of n (sample size for each group). But that's off the point. We had 5 papers in our class for psychology majors (I almost graduated in that instead of engineering) that discussed why controlled experiments (using the p-value) should not be published. In each case my knee-jerk reaction was that they didn't like math or didn't understand math and just wanted to 'suppose' answers. But each article attacked the math abuse, by proficient academics at universities who did this sort of research. I came around too. The math is established for random environments but the scientists control every bit of the environment, not to get better results but to detect thing so tiny that they really don't matter. The math lets them misuse the word 'significant' as though there is a strong connection between cause and effect. Yet every environmental restriction (same living arrangements, same diets, same genetic strain of rats, etc) invalidates the result. It's called intrinsic validity (finding it in the experiment) vs. extrinsic validity (applying in real life). You can also find things that are weaker (by the square root of n) by using larger groups. A study can be set up in a way so as to likely find 'something' tiny and get the research prestige, but another study can be set up with different controls that turn out an opposite result. And none apply to real life like reading the results of an entire population living normal lives. You have to study and think quite a while, as I did (even walking the streets around Berkeley to find books on the subject up to 40 years prior) to see that the words "99 percentage significance level" means not a strong effect but more likely one that is so tiny, maybe a part in a million, that you'd never see it in real life.

Comment: Re:Landing vs splashdown (Score 1) 340

All the engines on the Falcon 9 (and just about every other multiengine* rocket stage) are fed from the same propellant and oxidizer tanks. Giving them separate tankage just adds weight and plumbing complexity.

In the Falcon Heavy, there is a cross-feed mechanism from the outrigger 9s to the core so that the core can keep burning when the outriggers jettison (saving weight).

*(except multiengine solids, where the engine is the fuel tank.)

Comment: Re:Landing vs splashdown (Score 1) 340

DC-X also did it, several times -- but then DC-X wasn't trying to make even a fraction of orbit, it was proving the vertical takeoff and landing principle. Its engines (modified Pratt & Whitney RL-10s) could be more deeply throttled than the Falcon's Merlin, and it (the DC-X) was built fairly heavy to start with, since was designed as a test vehicle rather than a launcher (fully-fueled the legs couldn't hold its weight, it needed a support structure for takeoff -- and in an abort (happened once) it had to hover until it had burned off enough fuel to land).

Since then a number of small-company-built test vehicles have done the same, although not (afaik) to the tens of thousands of feet altitudes that the latter DC-X flights made.

Comment: Re:Landing vs splashdown (Score 2) 340

One would think that if they didn't know that the shuttle's boosters are made of inch-or-more-thick steel, while the Falcon's tanks are millimeter thick aluminum-lithium. And that the booster splashdown still tended to leave the boosters slightly out of round (which contributed to the problem Challenger had).

The extra fuel almost certainly weighs less than the necessary parachutes would.

Comment: Re:Refactoring done right happens as you go (Score 2) 247

by AJWM (#49178245) Attached to: Study: Refactoring Doesn't Improve Code Quality

"Memory architecture" -- you mean data structures?

As the title of my old intro CS text put it, "Algorithms + Data Structures = Programs". Yep, one is clearly going to influence the other, and sometimes a minor tweak in one will vastly simplify (or complicate, if you do it wrong) the other.

Refactoring isn't merely reformatting -- a prettyprinter can do that -- but it can help give you insight into the code. After getting the code right I like to refactor to see how much code or useless variables I can get rid of, but that's partly a hangover from my old APL one-liner days. (grin)

Comment: Re:This should not be on the front page (Score 1) 247

by AJWM (#49178203) Attached to: Study: Refactoring Doesn't Improve Code Quality

I could believe 10 kloc (kilo lines of code) functions being created by some front-end automated code generator (like a gui builder or parser generator, etc). If anyone is hand-coding 10 kloc functions they should be taken out and shot, or at least have their fingers broken so they don't do it again.

And while a multi-million-line class certainly seems excessive, that says nothing about how it's broken down into members and methods and inner classes.

Comment: Re:Roads are now illegal (Score 2) 199

You don't have to be actually breaking the law, the cop just has to have a reasonable suspicion that you might be.

Many, many years ago as a teenager I got stopped by an on-foot cop (I was pulling out of a fast food place). Turns out he recognized the license plate because the car (my mom's) had been stolen (for joy rides) several times before (easy to hotwire, and predating ignition locks in the steering column). I wasn't breaking any law, but the stop was justified on suspicion. Since the last name and address on my license matched the registration, of course he waved me on as soon as I'd shown them to him.

Comment: Re:so not only and ancient disease? (Score 4, Interesting) 65

by AJWM (#49124761) Attached to: Giant Asian Gerbils May Have Caused the Black Death

Plague is endemic to the prairie dogs of the Four Corners area of the US (where NM, Arizona, Utah and Colorado meet). Every year it gets transmitted to a few people. Presumably early diagnosis and antibiotics will take care of it, but occasionally it will go missed until too late.

Of bigger concern in that area is hantavirus.

Comment: Re:Nuclear fission has higher carbon than measured (Score 1) 309

by AJWM (#49107743) Attached to: The IPCC's Shifting Position On Nuclear Energy

Considering that I gave a paper on (in part) the use of a beanstalk on Mars in the 1991 Space Manufacturing Conference, and a similar one at the Case For Mars IV (or whichever) conference, I do know a bit about orbital tethers and doing a Mars version.

Since you were the one who mentioned running a mono (greek root, means "single" or "alone") filament to orbital satellites, you were the one implying a single stage version from the surface to (geostationary, unless you're planning on wrapping the planet like a ball of yarn).

Sure, there are other ways to do it. As you suggest, none of them are elegant.

Comment: Re:Yes we should but... (Score 1) 291

by AJWM (#49056637) Attached to: Should We Really Try To Teach Everyone To Code?

Troubleshooting is a skill applicable to, and learned in, far more than the narrow domain of coding. Your experience is biased by the crowd you hang out with in your chosen profession.

But any good mechanic (taking that as a generic term for electrician, plumber, etc also) is a good troubleshooter/problem solver, ditto any other expert in their chosen field (doctors, lawyers, salespeople, etc). It's a skill you need to be a good programmer, but it's a skill you need to be good at anything. How do I isolate the symptom? What is the real problem? What can I do to fix it? What can I substitute or change if I don't have the right part (library, API) to fix it as is?

I've seen plenty of coders who weren't that hot at troubleshooting (especially if it required some out-of-the-box thinking). I don't think coding teaches that skill, but it may well exercise it and make it stronger if it's already there.

365 Days of drinking Lo-Cal beer. = 1 Lite-year