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Posts

October 21, 2014

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3:00 AM | Robert Heinlein's house of the future
I was doing some research on Heinlein for a post in the compensation thread and I happened on this article on the house he and his wife (an engineer) designed and built in the early Fifties. For Heinlein fans it's a chance to see another side of the man. For the rest of us, it's an interesting glimpse into the way futuristic used to look.You can find the rest of the article here.

October 20, 2014

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10:00 PM | Network Theory (Part 32)
Okay, today we will look at the ‘black box functor’ for circuits made of resistors. Very roughly, this takes a circuit made of resistors with some inputs and outputs: and puts a ‘black box’ around it: forgetting the internal details of the circuit and remembering only how the it behaves as viewed from outside. As […]
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5:03 PM | The CMS PhD program
At the beginning of this year I wrote an excited post announcing our new Computing and Mathematical Sciences (CMS) PhD program.  Unfortunately, the approval did not happen in time for students to apply to it last year, but everything is up and running now, so we’re looking forward to seeing the first round of applicants […]
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4:28 PM | Network Data rates: Advertised Versus Actual
Introduction I often get questions from customers on what data rate can they expect from their particular network protocol, like Ethernet, MoCA, or HPNA. They often have expectations that have been set by marketing material and not reality. I thought … Continue reading →
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2:12 PM | Three ways to present a probability forecast, and I only like one of them
To the nearest 10%: To the nearest 1%: To the nearest 0.1%: I think the National Weather Service knows what they’re doing on this one. The post Three ways to present a probability forecast, and I only like one of them appeared first on Statistical Modeling, Causal Inference, and Social Science.
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1:43 PM | Einstein equation in the Newtonian limit
Reference: Moore, Thomas A., A General Relativity Workbook, University Science Books (2013) – Chapter 21; Problem 21.1. The Einstein equation is where we have yet to determine the constant . To do this, we need to show that the Einstein equation reduces to Newton’s law of gravity for weak gravitational fields. Actually, there are three […]
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1:00 PM | On deck this week
Mon: Three ways to present a probability forecast, and I only like one of them Tues: Try a spaghetti plot Wed: I ain’t got no watch and you keep asking me what time it is Thurs: Some questions from our Ph.D. statistics qualifying exam Fri: Solution to the helicopter design problem Sat: Solution to the […] The post On deck this week appeared first on Statistical Modeling, Causal Inference, and Social Science.
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11:03 AM | Big Data’s Disparate Impact
Take a look at this paper by Solon Barocas and Andrew D. Selbst entitled Big Data’s Disparate Impact. It deals with the question of whether current anti-discrimination law is equipped to handle the kind of unintentional discrimination and digital redlining we see emerging in some “big data” models (and that we suspect are hidden in a bunch more). […]
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5:30 AM | The World We Live In #2: To Study Or To Work
I was getting ready for school and about to wear my uniform when I remembered that our principal had told us not to wear uniforms. So I decided to wear my favorite pink dress (Malala Yousafzai) After reading the diary of a Pakistani schoolgirl and Malala’s history, there is no doubt of being in front […]
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4:30 AM | The myth of a data-driven Netflix
There's been a lot of talk about Netflix stock this week (usually with words like "plummet"), but a big part of the story has largely gone unnoticed, probably in part because it involves statistics.As mentioned before, some aspects of the Netflix narrative such as the company building and HBO type content library, are simply, factually incorrect. Others, while not blatantly wrong, are difficult to reconcile with the facts.One of the accepted truths of the Netflix narrative is that CEO Reed […]
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3:45 AM | Personification and pseudoscience
If you study the philosophy of science — and sometimes even if you just study science — then at some point you might get the urge to figure out what you mean when you say ‘science’. Can you distinguish the scientific from the non-scientific or the pseudoscientific? If you can then how? Does science have […]

October 19, 2014

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6:29 PM | A Small Low-Voltage Landscape Wiring Project
Introduction I have a small low-voltage lighting project that I want to put in my backyard, similar to what show in Figure 1. I have not done a significant low-voltage wiring project in quite a few years, so I decided … Continue reading →
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4:05 PM | Thoughts on Helen Keller
I must have seen something about Helen Keller on TV when I was a child. I do not exactly remember what it was and when her name recently came into my mind I could not remember what the story was. I just knew that she had an unusual handicap. Wikipedia confirmed my vague memory that […]
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3:51 PM | Sparse Representations, Numerical Linear Algebra, and Optimization Workshop
A couple of weeks ago, I attended the “Sparse Representations, Numerical Linear Algebra, and Optimization Workshop.” It was my first time at Banff, and I was thoroughly impressed by the weather, the facility, and the workshop organization. A few of the talks were recorded and are available here. Check out this good-looking group of participants:…
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3:05 PM | Watching Closely: Asteroids, Comets
Near-Earth Asteroid Discovery Statistics (h/t Ron Baalke)Twenty years ago, we watched an asteroid hit Jupiter with mostly Earth or orbital based telescopes. Today, we will have a comet past Mars and it will be watched by our robots on Mars, in less than a month, we will be harpooning another comet on a spot that needs a name, while Hubble continues to downselect potential asteroid by one of our spacecraft in the Kuiper belt. We live in interesting times.Watch live streaming video […]
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1:54 PM | “Your Paper Makes SSRN Top Ten List”
I received the following email from the Social Science Research Network, which is a (legitimate) preprint server for research papers: Dear Andrew Gelman: Your paper, “WHY HIGH-ORDER POLYNOMIALS SHOULD NOT BE USED IN REGRESSION DISCONTINUITY DESIGNS”, was recently listed on SSRN’s Top Ten download list for: PSN: Econometrics, Polimetrics, & Statistics (Topic) and Political Methods: […] The post “Your Paper Makes SSRN Top Ten List” appeared first on […]
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12:31 PM | Aunt Pythia’s advice
Quick, get on the bus! Hurry! Aunt Pythia is gonna be super fast this morning because she’s got crepes to make and apples to pick. Are you ready? Belts buckled? OK great, let’s do this. And afterwards: please think of something to ask Aunt Pythia at the bottom of the page! By the way, if […]
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7:46 AM | Doing Elitism Wrong
So, Katie Mack pointed me to this webcomic, which shows two characters stargazing. “I’m surprised more people don’t love science. It’s so fascinating.” “By science, do you mean spending countless hours collecting data and studying dense research articles? Or do you just think space is pretty?” OK. Let’s unpack the wrongness of this. (It’s been […]
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5:00 AM | Sunday Morning Insight: Crossing into P territory
This is a follow-up to the recent  Sunday Morning Insight on Escaping Feynman's NP-Hard "Map of a Cat": Genomic Sequencing Edition  To recap, in compressive sensing, it's been known for a while that some solutions can be found thanks to l_1 (P or Polynomial time) relaxation of combinatorial problems (NP). In fact, the whole field of compressive sensing took off when people realized one could be on the P side most of the time.In genome sequencing the latest long read technology have […]

October 18, 2014

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9:46 PM | Dimensional analysis and the Ebola epidemic
To follow up on my discussion of the Ebola uncertainty. Let's take a look at some very basic differential equations that we can use to get an idea of the factors that go into making up an epidemic. First, we'll model a population as having infected and uninfected . Let's also measure these populations as […]
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9:24 PM | Jest to Oberon
I can’t find my copy of The God Delusion. It wandered off to join the fairies in the Boston Public Garden, or something. This is only a problem when I’d like to look something up in it, to point to a passage and say, “Ah! If we’d read more carefully, we could have guessed that […]
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6:26 PM | Gravity can’t exist in 3 spacetime dimensions either
Reference: Moore, Thomas A., A General Relativity Workbook, University Science Books (2013) – Chapter 21; Problem 21.6. We’ve seen that the Einstein equation doesn’t allow gravity to exist in 2 spacetime dimensions. Here we’ll look at a demonstration that gravity also cannot exist in 3 spacetime dimensions of , and . Because of the symmetries […]
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6:06 PM | Gravity can’t exist in 2 spacetime dimensions
Reference: Moore, Thomas A., A General Relativity Workbook, University Science Books (2013) – Chapter 21; Problem 21.5. One consequence of the Einstein equation is that gravity cannot exist in a vacuum in a universe with fewer than 4 dimensions (3 space and 1 time). Here we’ll look at a demonstration of this for 2 dimensions […]
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5:36 PM | Einstein tensor of zero implies a zero Ricci tensor
Reference: Moore, Thomas A., A General Relativity Workbook, University Science Books (2013) – Chapter 21; Problem 21.2. We wish to prove that if and only if . The Einstein tensor is defined as   Clearly if the Ricci tensor then (since the curvature scalar is the contraction of the Ricci tensor: ). To prove the […]
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5:16 PM | Einstein equation for a perfect fluid
Reference: Moore, Thomas A., A General Relativity Workbook, University Science Books (2013) – Chapter 21; Problem 21.3. The Einstein equation can be written as For a perfect fluid the stress-energy tensor is where is the four-velocity, is the energy density and is the pressure. We have for the stress-energy scalar: since and in any coordinate […]
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5:04 PM | Drawing a Perpedicular Out in the Wild
My most satisfying applications of geometry occur in my construction projects. Previously, I have discussed how to find the radius of circle on construction projects. In this post, I will discuss four methods for constructing a perpendicular to a line. … Continue reading →
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4:29 PM | Einstein equation: alternative form
Reference: Moore, Thomas A., A General Relativity Workbook, University Science Books (2013) – Chapter 21; Box 21.3. The general relativistic generalization of Newton’s law of gravity is where the Einstein tensor is defined in terms of the Ricci tensor and the curvature scalar as We can write this in a different form that is sometimes […]
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1:43 PM | Hoe noem je?
Haynes Goddard writes: Reviewing my notes and books on categorical data analysis, the term “nominal” is widely employed to refer to variables without any natural ordering. I was a language major in UG school and knew that the etymology of nominal is the Latin word nomen (from the Online Etymological Dictionary: early 15c., “pertaining to […] The post Hoe noem je? appeared first on Statistical Modeling, Causal Inference, and Social Science.
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12:11 PM | Experts vs Professionals
Working with professionals can be a joy. Not only can they solve your problem, they may help you see what problem you should solve. I’ve had several instances lately when I hired a pro to do something I’d attempted myself. In each case I was very pleased and wondered why I hadn’t done this sooner. […]
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10:05 AM | Diminishing Differences Puzzle
Source: Australian Mathematical Society Gazette Puzzle Corner 34 Problem: Begin with n integers x1, . . . , xn around a circle. At each turn, simultaneously replace all of them by the absolute differences Repeat this process until every number is 0, then stop. Prove that this process always terminates if and only if n is a power of 2.
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