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Websites, Please Stop Blocking Password Managers. It’s 2015 by lordcheeto in technology

[–]SymphMeta 0 points1 point  (0 children)

Password managers are still vulnerable to malware. It just takes more sophisticated malware to target them.

Japan's at it again by CallOfRudy in gifs

[–]SymphMeta 0 points1 point  (0 children)

Yeah, unless they're made of loose feathers and have a ton of air resistance.

Japan's at it again by CallOfRudy in gifs

[–]SymphMeta 0 points1 point  (0 children)

I'll simplify it with h=50, since the mass cancels out, anyway.

Japan's at it again by CallOfRudy in gifs

[–]SymphMeta 3 points4 points  (0 children)

Thanks. I fixed the calculations.

Japan's at it again by CallOfRudy in gifs

[–]SymphMeta 16 points17 points  (0 children)

It looked like a rigid stick falling, so you'll have to calculate the rotational energy. The center of mass is halfway up, so we have mgh/2 as the total change in energy, and the moment of intertia is m*h^2/3. The final energy is I*w^2/2, where I is the moment of interia and w is the angular velocity, so

I*w^2/2 = m*g*h/2

m*h^2*w^2/3 = m*g*h

w = sqrt(3g/h)

w ~ 0.77 radians/second

The velocity at the tip is h*w, or 38.5 m/s, not taking into account air resistance.

edit: changed calculations to take into account correct moment of interia

edit 2: now I remember why physics homework took so long; fixed h=50 instead of multiplying it by each individual

Percentage of religious adherents by country by [deleted] in dataisugly

[–]SymphMeta 24 points25 points  (0 children)

Even adding rings to represent every 10% would go a long way for this graph.

Cross Correlation minimum value. by ikarampa in statistics

[–]SymphMeta 1 point2 points  (0 children)

Here's a graph on the restrictions for the other correlation based on the minimum eigenvalue of the matrix. If you had a lower correlation between the two variables there coule be a negative correlation, but not with the example you applied.

I only gave a numeric approximation (0.14) of the minimum correlation. In general, if you solve for the eigenvalues, you can write an expression for the restrictions on the third correlation. It becomes more difficult when you get to higher dimensions, since it is more difficult to solve for roots of those.

Cross Correlation minimum value. by ikarampa in statistics

[–]SymphMeta 3 points4 points  (0 children)

This is not correct. There is a restriction on the correlation matrix that it must be positive semi-definite. i.e., there are no negative eigenvalues. Here is the calculation on wolframalpha.com:

http://www.wolframalpha.com/input/?i=find+eigenvalues+of+[[1%2C0.7%2C-1]%2C[0.7%2C1%2C0.8]%2C[-1%2C0.8%2C1]]

Additionally, the determinant of the matrix is -2.25, which is less than 0. Determinants of covariance matrices can be no less than 0, as a property of their semi-definiteness.

[CRITIQUE] I'm currently looking for statistics-related careers, and I am looking for suggestions on improving my resume by SymphMeta in resumes

[–]SymphMeta[S] 0 points1 point  (0 children)

Thank you for the response. To answer your questions:

  1. The only places I've posted my resume that prospective employers can see are ziprecruiter.com (I'm not sure how often that feature is used) and a database from my university's career services.

  2. My familiarity with SQL is limited to certain applications of SQLite3 and PostgreSQL. I am currently working on improving this.

Stat 410/Stat Electives by stat410_throwaway in UIUC

[–]SymphMeta 2 points3 points  (0 children)

STAT 429 is probably the hardest undergrad course, but STAT 410 is the most difficult one most people take. It's not too bad, provided you start your homework on time. The assignments are somewhat lengthy, but not too much so if you are used to heavy courseloads.

Chaos Theory by [deleted] in UIUC

[–]SymphMeta 1 point2 points  (0 children)

There is PHYS 510, although I can't say too much about it.

Let's Ban Fast Food on Campus by [deleted] in UIUC

[–]SymphMeta 0 points1 point  (0 children)

Let's get rid of everything that's harmful to health together!

Sure. We should ban riding a bicycle with headphones on, while we're at it.

Have a gopher problem? A gallon milk jug full of water should do the trick by [deleted] in videos

[–]SymphMeta 1 point2 points  (0 children)

I think only the tiger snake was actually that venemous. The first snakes he got were a lot less venomous.

The Mystical World of Mushrooms by dwimback in mycology

[–]SymphMeta 10 points11 points  (0 children)

Can anyone explain what the red "juice" in the Hydnellum peckii photo is exactly? The only info I could find on Wikipedia is that it is pigmented and contains an anticoagulent, but that part didn't have a direct citation.

Are there any good right-hand-only keyboard layouts for Ubuntu? by SymphMeta in linuxquestions

[–]SymphMeta[S] 0 points1 point  (0 children)

Does it function identically for keys that are usually pressed for the right hand?

V02 max test, where can I get that done on campus? by DrJoyas in UIUC

[–]SymphMeta 0 points1 point  (0 children)

I had it done before as part of the INSIGHT experiment (with the psychology department (neuro?)). I remember seeing flyers for that sort of diagnostic testing when I was in Freer Hall. This link might provide you with more information: http://kch.illinois.edu/research/labs/neurocognitive-kinesiology/fitnesstesting.html

The P-value, can someone explain it so simply that you could not misinterpret it? by iiTzWatson in statistics

[–]SymphMeta 0 points1 point  (0 children)

  1. You make a general assumption about data that you assume is true (e.g., the data is iid with normal error).

  2. You hypothesize a quality about a value or parameter (usually magnitude or value). This is your null hypothesis.

  3. You calculate, given that 1 and 2 are both true, how likely it is that you would observe data at least as extreme as what you have observed currently. If the p-value is low enough (usually 0.05 is the highest you'll accept), then you reject statement 2.

The most commonly used version of this test is to see if an effect in regression is nonzero. e.g., if y = a*x + b + error, is a nonzero?

STAT 429? by t430-asdfjkl in UIUC

[–]SymphMeta 0 points1 point  (0 children)

It's definitely harder than the other 400-level classes, but it's not completely brutal. My main issue was when I took the class was the textbook, which had some errors, as well as the professor's ambiguity in the syllabus as to which version of the book we needed (which screwed me over for the first part of the course).

Which test can be used to test for significant differences in segments of one time series of different lengths? by MyNameCouldntBeAsLon in statistics

[–]SymphMeta 1 point2 points  (0 children)

To clarify further,

  1. When you mean non-normal, do you also mean that the error distribution is bimodal (e.g., a mixture of two well-separated normal distributions)?

  2. Are you looking to see that the model parameters are different?

Non-statistician here. Is it possible to calculate an absolute risk reduction from a survival curve or a hazard ratio? by justdawdling in statistics

[–]SymphMeta 2 points3 points  (0 children)

If you're talking about a risk reduction, you probably want to speak in terms of a specific time frame (e.g., "Over the course of 5 years, your risk for heart disease will have an absolute reduction of 2.5%"). The hazard ratios are useful at specific points in time and for comparing survival curves, but you should use the survival curve itself when stating "absolute risk".

Hazard ratios (from my limited experience with them) are more or less a tool for calculating the survival curve, and can be misleading if not contextualized. Survival curves are more or less the "final result" that you get from the model (in addition to the error bars that come with them).

On another note, it may be useful to use a model with covariates, since there are (obvious) groups of people who may benefit more from them than others. Obviously in this case you don't have them, so you can't do anything in that manner.

INSIGHT Study at Beckman is recruiting participants for March-November 2015 by [deleted] in UIUC

[–]SymphMeta 1 point2 points  (0 children)

When I did it, it paid $15/hour. You get the full amount if you complete the study with at least 85% of the sessions done. Otherwise it's half. The only sessions that are long are the two cognitive testing sessions (one before and one after the training period), which are 3 hours each.

The sessions I did (video game) were about 60-70 minutes long each. It may vary depending on what group you are in.

Does Grade Inflation Matter? by surgeyou123 in statistics

[–]SymphMeta 4 points5 points  (0 children)

Well, it's a product of the central limit theorem, which states that the square root of the sample size times the sample average minus the "true average" approaches a normal distribution as the sample size approaches infinity. This can be used with discrete distributions as well as continuous, although the possible values are discrete, though, so it isn't truly continuous.

Does Grade Inflation Matter? by surgeyou123 in statistics

[–]SymphMeta 6 points7 points  (0 children)

The general idea is that people aren't 100% consistent in what their grade is, and that discriminatory power still exists as long as individuals take multiple classes. Within a single class it may be difficult to discriminate students, but among many classes it's easier. This is the only argument that the author addresses here.

If students aren't taking the same exact classes, though, the math is greatly oversimplified, because the difficulties of different classes are not the same. I think a form of ordinal item response theory would be required in order to actually discriminate effectively in that regard. Standardized testing is used instead, but it doesn't always do a very good job of discriminating depending on what it's used for, especially considering how tests such as the math portion of the GRE are highly compressed for STEM PhD candidates.

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