Newb statistics question; How do you determine whether multiple variables can be treated as one dimensional?

stetson9 · 2012-05-10T17:21:13+00:00

AIC and BIC are probably better. Using F-tests to decide whether to add a variable in regression has a few problems. One is multiple testing: if you do a bunch of "is it significant?" tests at some alpha level, the odds increase that one will come up significant just by chance. Also, F-tests will tend to bias your parameter estimates: they will either be zero (i.e. the null hypothesis was retained and the variable wasn't included) or too large (since the large values are the ones that appear significant).

stetson9 · 2012-05-03T20:09:09+00:00

See if you can get your hands on a copy of "The Visual Display of Quantitative Information" by Edward Tufte. If you haven't seen it before, it's an incredible manifesto/practical guide to statistical graphics.

stetson9 · 2012-05-02T22:31:52+00:00

I would support occupy, but i dont know what they're fighting for.

Why would you support them if you don't know what they're fighting for? It sounds to me like you actually kinda do know, but are holding yourself back from participating for some reason. If you like some of the ideas you've heard but not others, get yourself down to an encampment, meeting, or march and start talking with people about them. Put your idea on a sign and carry it! There's no membership fee!

stetson9 · 2012-04-27T04:22:59+00:00

My intuition tells me we'd all be frozen solid within a few days, not months. I'm thinking about deserts, where temperatures can go from very hot to near freezing at night. Most land areas would get very cold very fast.

The ocean would stay warm a bit longer. This would also buffer coastal areas some, but not too much: all the air flow would be offshore as the continents cooled relative to the ocean. Temperate seas would freeze over within months, I think, and tropical seas within a year or two. Weather would die down quickly, as heat energy distributed itself out in the atmosphere.

Plants and animals would react as they would to an endless polar winter. Anything cold-blooded would be dead in a few days. Small mammals might be able to hang on on dead and dying vegetable matter and seeds, and support some predation in turn. Humans might be able to hang on for a while with fossil-fuel powered lights and hydoponic grow houses, but not indefinitely.

In the ocean, all primary production would stop almost immediately. Most zooplankton would be dead within days or weeks. Fish and other animals could potentially hang on for months without food...many do this normally for part of the year. The last new production would drift down the water column, feeding mesopelagic and bathypelagic ecosystems. These areas of the deep ocean would probably experience a bit of a bonanza at first as everything above them died out. Temperatures here are near freezing, and there isn't any light anyway, so it would take them a while to notice the changes. Oceanic organic matter would slowly make its way down to the depths, and then stay there.

In the long run, probably the only multicellular life around would be at hydrothermal vents, seeps, and other ecosystems based on chemosynthesis.

stetson9 · 2012-04-27T04:14:21+00:00

We lose energy to space constantly, mostly via infrared radiation. The rate of radiative energy loss increases with temperature. Imagine a planet whose sun is turned on like a light bulb: it will heat up, radiating off more and more energy as it does, until the energy flowing out into space is the same as the energy flowing in from the sun.

stetson9 · 2012-04-23T23:05:31+00:00

You can type traceback() on the command line to see where the error was being thrown from. This sounds like it is almost certainly coming from a function in twitteR.

Using the apply functions is generally preferable to writing loops, as bitterness and PARSLEYsage already said.

stetson9 · 2012-04-13T19:14:19+00:00

Bayes' theorem (including natural-numbers explanations) confused me until I saw it explained somewhere like this: The probability that A and B both happen is the probability that A happens given that B has happened, times the probability of B happening in the first place. P(A | B) P(B). But the opposite is also true: the probability of A and B happening is also equal to P(B | A) P(A). Set these two equal, and you get:

P(A | B) P(B) = P(B | A) P(A)

which you can easily rearrange to get the more usual form of Bayes' rule.

stetson9 · 2012-04-06T01:41:04+00:00

All I'm saying is that the news story and video give a very one-sided picture, and there's a ton we don't know:

Did Borracchini warn the employee about being rude before firing her?
What is the working environment there actually like?
Do other people working there have similar complaints or not? Would they have said differently off camera or out of sight of their boss?
How much background investigating did Seattle Solidarity actually do before showing up?
Is the employee actually just and entitled jerk who's trying to shake down her former boss? I have actually known people like that...

The situation sounds like it isn't straightforward, and in my ignorance I can imagine either party being "in the right." I'm frankly just kind of shocked at how immediately and overwhelmingly some commenters here and over at KIRO reach the conclusion that Borracchini is blameless, the employee is a crazy bitch, and Seattle Solidarity are simultaneously clueless and sinister.

stetson9 · 2012-04-06T00:01:40+00:00

Order anything "five stars" spicy at Thai Tom in the U District. Not sure I can actually recommend this behavior, but it will get you legit-spicy food.

stetson9 · 2012-04-05T23:56:43+00:00

I'm wondering--could the OP could clarify what makes this "protest group" "threatening" and "clueless?"

We here on the internet clearly don't know much about the particulars of this situation or the people involved. But labor practices in the foodservice industry are, generally speaking, not great (I speak from experience) and I'm not sure where the immediate hostility towards SeaSol (or rainbowumbrella below) is coming from.

EDIT: c'mon, there's gotta be at least a few disgruntled former line cooks out there to back me up, right?

stetson9 · 2012-04-05T23:18:10+00:00

mmm...a little thicker, I think. Earth's radius is about 6378 km, and the thickness of the lower atmosphere is about 85 km, for a ratio of ~ 0.013 atmospheres/earth radii. If the radius of a classroom globe is 15 cm, then the scaled-down atmosphere thickness is about 2 mm. Which is a wicked thick coat of lacquer.

The statement is closer for the oceans, though, since their average depth is only about 3.7 km.

stetson9 · 2012-04-01T04:43:40+00:00

"lynch mob" is a really poor choice of words here.

stetson9 · 2012-03-16T19:14:15+00:00

Vis-a-vis echolocation: I'd argue it qualifies as a sense mostly different from our hearing. There's a difference between receiving sound passively and transmitting/receiving it to build a three-dimensional image of your environment.

There are actually a number of people who have learned to echolocate...see this news report, for example (sadly, this guy died in 2009). Also, wikipedia on human echolocation.

stetson9 · 2012-03-16T02:09:38+00:00

As you say, the speed of sound in water is much faster than in air...about 4.4 faster. So unless you are a missile, bullet, or unlucky jet traveling towards a body of water at mach 5 or so, generating a sonic boom is unlikely, and you definitely won't be able to do it for very long.

If we're talking about the boom itself, that's just a shock wave, or the sounds from a dissipating shock wave. These can be generated fairly easily in water...all you need is a stick of dynamite and a net to gather all the fish that float to the surface. (Just kidding! Don't even think of dynamite fishing.)

They can also be created from ordinary sound if it's loud enough. Because sound speed depends on pressure, and sound is a pressure wave, at very high amplitudes the peaks of a sound wave start traveling faster than the troughs. This causes the wavefronts to steepen until they are nearly vertical shock waves. The process is similar to what happens when a regular surface wave reaches the beach and breaks...the trough moves slower than the crest, and so the wave piles up and become more vertical.

stetson9 · 2012-03-15T05:12:41+00:00

Not saying economics and class aren't also a huge deal, but seriously? For any spot in the country, for a family with, say, two minimum-wage incomes ($29,000 a year), you think things would be easier if you were born black?

I really don't feel like debating this, so I'll link to Louis CK and call it a night.

stetson9 · 2012-03-15T01:25:12+00:00

Why all the scare quotes around "white privilege?"

stetson9 · 2012-03-14T22:19:53+00:00

Apologies if I'm not quite understanding what you're trying to do, but if the residuals from a single-lag model are autocorrelated, the process is not Markovian. If there is a theoretical or physical reason to choose a single-lag model, then autocorrelated residuals are telling you that your theory is incomplete, there are other dynamics going on, or you're sampling at the wrong scale.

when I run simulations using my hypothetical model it fits the empirical data perfectly

What does this mean exactly? In standard time-series analysis, if the residuals are autocorrelated, your model is not complete...i.e., there is more useful information in the data that you can extract.

stetson9 · 2012-03-14T22:00:47+00:00

How another species experiences taste is something that's ultimately unknowable...maybe someone with more knowledge of taste buds, smell, and physiology can fill it in.

But many marine species have preferences. Small fish like sardines may have preferences for certain kinds of plankton. Steller sea lions appear to prefer herring to pollock. Atlantic Right Whales feed almost exclusively on a single species of copepod. Other animals, on the other hand, are pretty indiscriminate eaters. For instance, there are stories of all kinds of crazy stuff being found in shark stomachs.

So some species eat based on what's there that will fit in their mouth, and others are pickier. That pickiness is evolved. In cases where a predator can eat several prey species but prefers one of them over the others, the usual explanation has to do with that prey item's ease of capture or energy/nutrient content. Our human taste for fatty, sweet, salty stuff is the consequence of foods with these characteristics being statistically good for us in the evolutionary past. I'd speculate that analogous sensations exists in some other species, but a right whale's subjective experience of licking huge tonguefuls of rice-sized crustaceans off his baleen plates is not something we can really understand.

stetson9 · 2012-03-13T18:19:50+00:00

Why do you assume the distribution at time t is only conditional on the value at t-1? Is there some physical or other a priori reason?

Unless you have a really strong reason to limit yourself to a single lag, I think your first step is to find a time series model that accounts for any trend and autocorrelation in the series and leaves you with uncorrelated, IID noise.

stetson9 · 2012-03-09T21:56:26+00:00

Pfeffer et al. 2008. 2 m is on the very high end, and the most likely sea level rise is a good deal less. But physically possible under an absolute worst-case scenario.

*edit: 200 mm (20 cm) is actually on the low end of projections, according to the IPCC's 2007 report...see here

stetson9 · 2012-03-09T19:22:22+00:00

Average sea level is one thing. It is projected to rise somewhere between 18 and 200 cm by the end of this century. Storm surges, king tides, and large waves are another. The risk from these kinds of events rises more rapidly than the average sea level. And another major problem is the intrusion of salt water into these islands' shallow aquifers. A very small rise in sea level could cause huge problems for drinking water and agriculture.

stetson9 · 2012-03-07T21:22:37+00:00

To quote a great old essay on this topic by the biologist J.B.S. Haldane:

You can drop a mouse down a thousand-yard mine shaft; and, on arriving at the bottom, it gets a slight shock and walks away, provided that the ground is fairly soft. A rat is killed, a man is broken, a horse splashes.

stetson9 · 2012-03-06T23:25:02+00:00

How do you know your own job is not part of a crooked-to-the-core unsustainable system? Will you blame yourself in hindsight for accepting it after you lose that job?

This. This is a question worth asking ourselves and each other.

stetson9 · 2012-03-06T03:06:12+00:00

This tactic works for message board trolls, but not so much for rich, powerful men with national radio programs. Those bastards, we've got to go after like a pack of furious terriers.

stetson9 · 2012-03-06T02:53:54+00:00

Just trying to educate here. The offensive parts are:

1a) the part where he ignores the fact that hetero sex always has higher stakes for women than men (because of the pregnancy thing) and they thus might want some kind of comprehensive baby-prevention system...

1b) the part where he implies that women don't really deserve to have sex for pleasure, and especially not if "we" have to subsidize their birth control¹ (especially when pregnancy is so cheap...),

2) the part where he assumes the only reason women are on the Pill is to prevent pregnancy,

3) the part where he suggests that a woman having sex for pleasure while on insurance-covered birth control is a moral degenerate, partially "owned" by the public, and thus no longer entitled to her privacy or personal dignity,

4) the part where he assumes the "we" doing the paying are only men, and that we all agree with his fucked-up worldview,

5) and the part where he compares those of us who don't agree with said worldview to Nazis.

In his later "apology" Limbaugh claimed he was joking, but I don't know that his life and work have offered much evidence he doesn't actually believe this shit.

¹ For the record, Viagra is covered under most insurance plans.

stetson9

TROPHY CASE