Playing-With-Graphs
drorzel | April 18, 2012Yesterday's post on applying intro physics concepts to the question of how fast and how long football players might accelerate generated a bunch of comments, several of them claiming that the model I used didn't match real data in the form of race clips and the like. One comment in particular linked to a PDF file including 10m "splits" for two Usain Bolt races, including a complicated model showing that he was still accelerating at 70m into the race. How does this affect my argument from yesterday?
Well, that document is really a guide to fancy fitting routines on some sort of graphing…
drorzel | April 17, 2012Over at Grantland, Bill Barnwell offers some unorthodox suggestions for replacing the kickoff in NFL games, which has apparently been floated as a way to improve player safety. Appropriately enough, the suggestion apparently came from Giants owner John Mara, which makes perfect sense giving that the Giants haven't had a decent kick returner since Dave Meggett twenty years ago, and their kick coverage team has lost them multiple games by giving up touchdowns to the other team.
Anyway, one of Barnwell's suggestions invoked physics, in a way that struck me as puzzling:
Idea 3: The receiving team…
drorzel | March 19, 2012I'm trying not to obsessively check and re-check the Dog Physics Sales Rank Tracker, with limited success. One thing that jumped out at me from the recent data, though, is the big gap between the book and Kindle rankings over the weekend. The book sales rank dropped (indicating increased sales, probably a result of the podcast interview), while the Kindle rank went up dramatically. This suggests that people who listen to that particular podcast are less likely to buy new books on the Kindle than new books on paper.
This got me wondering, though, whether this was an anomaly, or a general truth…
drorzel | February 29, 2012One of the big stories in genre Internet news was Seanan McGuire's post last week, about reactions to the early release of some copies of her book, and the hateful garbage thrown her way by people outraged that the ebook didn't slip out early as well. And let me state right up front that the people who wrote her those things are lower than the slime that pond scum scrapes off its shoes. That's absolutely unconscionable behavior, and has no place in civilized society.
That said, Andrew Wheeler picked up on something that also struck me as odd, namely the way McGuire was so upset about paper…
drorzel | January 19, 2012In the same basic vein as last week's How to Read a Scientific Paper, here's a kind of online draft of the class I'm going to give Friday on the appropriate ways to present scientific data. "Present" here meaning the more general "display in some form, be it a talk, a poster, a paper, or just a graph taped into a lab notebook," not specifically standing up and doing a PowerPoint talk (which I've posted about before).
So, you've made some measurements of a natural phenomenon. Congratulations, you've done Science! Now, you need to tell the world all about it, in a compact form that allows the…
drorzel | January 2, 2012My class this term is a "Scholars Research Seminar" with the title "A Brief History of Timekeeping," looking at the science and technology of timekeeping from prehistory through modern atomic clocks. This is nominally an introduction to "research methods," though the class operates under a lot of constraints that fully justify the scare quotes, at least for scientists. As I am a scientist, though, I want the class to include at least one original measurement and the reporting thereof, so I've been thinking of really simple measurements that I can have them do independently and write up. I've…
drorzel | November 22, 2011A few months back, I did a post about estimating the time required for the different routes I take to work, looking at the question of whether it's better to take a shorter route with a small number of slow traffic lights, or a longer route with a bunch of stop signs. This was primarily conceived as a way to frame a kinematics problem, but I got a bunch of comments of the form "Aren't you an experimentalist? Where's the data?"
Well, here it is:
This is a histogram plot showing the number of times my morning commute fell into a given ten-second bin over the last couple of months. The blue…
drorzel | August 12, 2011I am an inveterate driver of "back ways" to places. My preferred route to campus involves driving through a whole bunch of residential streets, rather than taking the "main" road leading from our neighborhood to campus. I do this because there are four traffic lights on the main-road route, and they're not well timed, so it's a rare day when I don't get stuck at one or more of them. My preferred route has a lot of stop signs, but very little traffic, so they're quick stops, and I spend more time in motion, which makes me feel like I'm getting there faster.
That's the psychological reason, but…
drorzel | August 10, 2011The other big gender-disparity graph making the rounds yesterday was this one showing the gender distribution in the general workforce and comparing that to science-related fields:
This comes from an Economics and Statistics Administration report which has one of the greatest mismatches between the tone of the headline of the press release and the tone of the report itself. Nice work, Commerce Department PR flacks.
There are a couple of oddities about this report, the most important being that they appear to have excluded academics from the sample, though that probably depends on how people…
drorzel | August 10, 2011There are two recent studies of gender disparities in science and technology (referred to by the faintly awful acronym "STEM") getting a lot of play over the last few days. As is often the case with social-science results, the data they have aren't quite the data you would really like to have, and I think it's worth poking at them a little, not to deny the validity of the results, but to point out the inherent limitations of the process.
The first is a study of lifetime earnings in various fields that includes this graph showing that women with a Ph.D. earn about the same amount as men with a…
drorzel | July 19, 2011A lot of pixels have been spent discussing this study of grade inflation, brought to most people's attention via this New York Times blog. The key graph is this one, showing the fraction of grades given in each letter category over the last fifty years:
Lots of effort is being put into trying to explain why the number of A's given out has increased so much over this time span, with most of it focussing on the last twenty years or so (see Mad Mike for a plausible but wrong explanation-- the fraction of students going on to graduate school isn't big enough to drive this). I think this is…
drorzel | July 14, 2011I really ought to be doing other things, but this roller slide business kept nagging at me, and I eventually realized I could mock up a crude simulation of the results. This led to the production of this graph:
This looks pretty similar to the Tracker Video data from the previous post, which I'll reproduce below the fold, along with an explanation of the math that went into the model:
The two graphs are qualitatively similar, other than, you know, the godawful Excel aesthetic of the simulation results graph. One line looks relatively straight, like motion at constant speed, while the others…
drorzel | July 14, 2011On Monday, I posted a short video and asked about the underlying physics. Here's the clip again, showing SteelyKid and then me going down a slide made up of a whole bunch of rollers at a local playground:
The notable thing about this is that SteelyKid takes a much, much longer time to get down the slide than I do. This is very different than an ordinary smooth slide, where elementary physics says we should go down the slide at the same rate, and empirically I tend to be a little slower than she is.
So what's the difference?
First of all, let's be a little more quantitative about this. Here's…
drorzel | July 12, 2011A month and a half ago, I reported on a simple experiment to measure the performance of a timer from the teaching labs. I started the timer running at a particualr time, and over the next couple of weeks checked in regularly with the Official US Time display at the NIST website, recording the delay between the timer reading and the NIST clock.
As a follow-up experiment, I did the same thing with a different timer, this one a Good Cook brand digital timer picked up for $10 in the local supermarket, and the same Fisher Scientific stopwatch/timer as the first experiment, with the Fisher…
drorzel | July 11, 2011We took SteelyKid to the playground at one of the local elementary schools on Sunday morning. this one includes an odd sort of slide, made of dozens of rollers that are 1-2 inches in diameter (they're all the same size-- the range is just because I didn't measure them carefully). They're on really good bearings, and while it's kind of noisy, it's a reasonably smooth ride.
There is, however, one slightly mysterious aspect to this slide, clearly visible in this video that Kate was good enough to shoot for me:
SteelyKid takes something like 6 seconds to go down the slide, while it only takes me…
drorzel | July 10, 2011This morning, via Twitter, I ran across one of the most spectacular examples of deceptive data presentation that I've ever seen. The graph in question is reproduced in this blog post by Bryan Caplan, and comes from this econ paper about benefits of education. The plot looks like this:
This is one panel clipped out of a four-part graph, showing the percentage of survey respondents reporting that they are satisfied with their current job. The horizontal axis is the years of schooling for different categories of respondents.
So, I looked at that, and said "Wow, people with more education are…
drorzel | July 6, 2011Today's Links Dump came late because I was at the meeting of the APS's Committee on Informing the Public. We apologize for the inconvenience, but I was too busy acquiring this critically important scientific data:
What is that, you ask? It's this:
That's the Superman roller coaster at the Six Flags America park outside of DC, which is where we're meeting this time. Lots of amusement parks do Physics Days as outreach programs, so we did the Physics Day thing ourselves, wearing ugly blue vests holding accelerometers on the major rides. Of course, the vest-mounted accelerometer I was wearing…
drorzel | May 26, 2011As I've mentioned before, I'm schedule to teach a class on "A Brief History of Timekeeping" next winter term as part of the Scholars Research Seminar program. Even though I have a hundred other things to do, I continue to think about this a lot.
One of the goals of the course is to introduce students to the idea of doing research. This was primarily conceived as a humanities/ social sciences sort of thing, so most of the discussion I've seen about these has been in terms of library research. Of course, as a physicist, I very rarely need to look things up in the library. when I think about…
drorzel | April 22, 2011A few months ago-- just before the paperback release of How to Teach Physics to Your Dog-- Amazon started providing not only their Sales Rank data, but also sales data from Nielsen BookScan. Of course, the BookScan data is very limited, giving you only four weeks, and the Sales Rank data, while available over the full published life of any given book, are presented as a graph only with no way to extract them as a data table. You'd have to be some sort of obsessive nerd to make a quantitative comparison between them.
So, anyway, here's the data I got for How to Teach Physics to Your Dog:
This…
drorzel | March 22, 2011Kevin Drum re-posts a chart on wind power made by Stuart Staniford showing that the number of new wind power plants installed in 2010 was way lower than in 2009 or 2008:
This is meant as a starting point for discussion about the big economic issues that might've caused this. One of the many, many reasons I'll never make it as a political pundit, though, is that when I see a graph like this, I'm inexorably drawn to speculating about aspects of it that really have nothing to do with the intended point. In this particular case, I look at this graphic and ask myself "Why are there so many wind…