Comments, observations and thoughts from two bloggers on applied statistics, higher education and epidemiology. Joseph is an associate professor. Mark is a professional statistician and former math teacher.
As mentioned before, there are a couple of food-related megathreads in the queue, one on living on SNAP and one on the drought. Between those and the various posts we’ve run over the years, that’s a pretty big word count, so I decided to try a pop-up blog.
One of the disadvantages of eclectic blogging is that your target audience has to have compatibly eclectic tastes. By pulling all of the posts on one broadly appealing subject, I might just attract some readers who are interested in food and agriculture but aren’t interested in epidemiology, pedagogy, math puzzles, space travel, marketing statistics, bad business models, silly economic theories, education policy, games, negligent journalists, ddulites, old television shows, fitness landscapes, driverless cars...
A Statistician Walks into a Grocery Store will mainly consist of posts that have appeared or will appear here, so regular readers don’t have to add another link to their blog lists unless they have enough of a special interest in the topic to seek out the pieces too trivial to cross-post...
(I have a really tasteless joke on this one, though some of you will see it coming.)
I've been meaning to do a deep dive into how the language of the reform movement reflects its close connection with management consulting. If you've ever heard one of these consultants making a pitch to a high level executive, you may have noticed that while the words always have the connotation of precision and scientific rigor, the statements tend to be vague and inconsistent.
Diagnostic data needs to be specific and (to borrow a term from the business lexicon) actionable. It should also generally be multidimensional. On the individual student level, the tests being discussed here are not diagnostic data -- the results are neither timely nor specific enough to be actionable -- but Tisch suggests they are there to provide that level of information.("It is natural for parents to want to know how their kids are doing").
HAYES: OK. But there’s a whole — let’s sort of bracket the sociology of poverty for a moment… there’s lot of things I could contest about in what direct the causation of that link flows, right? But here’s the question to you, Miss Ravitch…I had someone who works in education who I respect compare testing opt out to people opting out of immunization, because basically it was like, look, yeah, your kid is probably not going to get measles and, like, if you think there’s some downside you can opt out, but then you’re just a free rider because the policy as a whole is a necessary means of figuring out where people are, assessing, right? You need this data.
If you start allowing people to opt out, you’ve just destroyed the entire dataset. Like, what are they going to do in West Seneca to judge anything year over year when one year they have data and the next they don’t have any data?
DIANE RAVITCH: It’s totally inappropriate to compare opting out of testing to opting out of immunization. One has a scientific basis, the other has none. The tests that kids take today have nothing to do with the tests that we took when we were kids. When we were kids, we took an hour test to see how we did in reading, an hour test to so how we did in math. Children today in third grade are taking eight hours of testing. They’re spending more time taking tests than people taking the bar exam.
Now, when we talk about the results of the test, they come back four to six months later. The kids already have a different teacher. And all they get is a score and a ranking. The teachers can’t see the item analysis. They can’t see what the kids got wrong. They can’t — they’re getting no instructional gain, no possibility of improvement for the kids, because there’s no value to the test. They have no diagnostic value.
If you go to a doctor and you say, ‘I have a pain,’ and the doctor says, ‘I’ll get back to you in six months,’ and he gets back to you and tells you how you compare to everyone else in the state, but he doesn’t have any medicine for you.
HAYES: Respond to that.
TISCH: Well, I would say that the tests are really a diagnostic tool that is used to inform instruction and curriculum development throughout the state. New York State spends $54 billion a year on educating 3.2 million schoolchildren. For $54 billion a year I think New Yorkers deserve a snapshot of how our kids are doing, how our schools are doing, how our systems are doing. There is a really important data point…
HAYES: Wait. … I just want to point out something. That was interestingly nonresponsive to what she said, right? She’s saying this does not work as diagnostic tool for the child or for the teacher, you’re saying this is a diagnostic tool for the taxpayer who is funding the system to see if the system is working, right? Those are distinct.
TISCH: No, let me finish because we’re talking about what happens when parents opt out and what the system can then report back to parents and to the state. The point of the matter is, you know, two weeks ago I was with my grandson at a pediatric visit. There was a new mother sitting next to me and she was comparing growth charts for her 4-month-old son. She wanted to know how he was doing on a continuum.
It is natural for parents to want to know how their kids are doing. And as for the diagnostic nature of these tests and the amount of
information that is gleaned from them, school districts report to us all the time that they design curriculum around the results of these tests.
I agree with Diane. There is no such thing as a perfect test, absolutely not. But the ability to glean information from these tests and
use them in very direct ways to inform instruction and curriculum in classrooms is actually really important.
If these tests aren't diagnostic, what are they? Mike the Mad Biologist has a suggestion:
What Ravitch touches on, but I wish had made more clearly, is that these tests are not about assessing individual students. The rhetoric Tisch uses is disingenuous, as the tests can not–as a matter of education policy and contractual obligations with test providers–to tell individual students (and their teachers and parents) where they need to improve.
The tests exist solely to grade teachers. These are not educational tools, as Ravitch notes, but managerial ones. They are used to hire and fire teachers. That is why the NY Department of Education is panicked by the opt-out movement. It’s not the potential inability to assess state-wide or even school level student performance (certainly for the former, there are enough students in the state of New York taking the exams for the statistics to work).
No, it’s the possibility that the state won’t be able to evaluate individual teachers with the exams. I’ve discussed many times before how sample size issues make teacher evaluations incredibly imprecise and are inappropriate in hiring and firing decisions. Imagine if a significant number of teachers can’t be evaluated because too few of their students decide to take the tests (there aren’t a whole lot of strong conclusions that can be reached if only eight students per class take the tests). It certainly would give grounds for teachers to challenge the conclusions drawn from the tests.
What Tisch doesn’t want to say out loud, what she politically can’t say out loud, is that she, along with many other reformers, believe if only we could fire the bad teachers–and she believes there are a lot of them–then our educational problems would vanish. But many reformers, having realized the majority of parents* don’t believe this, understand they can’t explicitly make that claim. So they lie about why we supposedly need annual high-stakes* testing.
A good brief overview of the main criticisms of standardized tests. Very entertaining and yet more balanced and thoughtful than what you would normally see in more "serious" formats.
Pay close attention to the opening segments. We'll be coming back to the analytic importance of keeping not just the content but the conditions and the incentives of these tests standardized. (Remind me to use the blood pressure analogy.)
I had actually forgotten how on-topic this video was.
As mentioned before, there's a thread coming up on hunger in this country prompted by yet another journalist who would apparently drop dead of malnutrition if she had to live on a budget for an extended period.
A big part of this story is the way different classes perceive budgets and shopping and the way most journalists have internalized upper and upper-middle class perceptions. It's telling that when a journalist had to find the cheapest place to buy food, she thought of Trader Joe's rather than a warehouse grocery like Food-4-Less or Aldi (which actually owns Trader Joe's but it's a very different brand).
Don't get me wrong. I shop at Trader Joe's all the time -- It's convenient, it's reasonable and the store brands are excellent.-- but if I were trying to feed myself on less than thirty dollars a week, I would shop there less.
A big part of the secret to the chain's success lies in its ability to offer pretty good bargains while maintaining its foodie street cred. The stores tend to cater to upscale, urban singles and couples whose cooking often consists of throwing frozen dinners in a microwave. Trader Joe's has discovered that, if you make these dinners seem a bit fancier or more exotic, your customers will feel more like urban sophisticates and less like pathetic losers.
I'm about to start another thread on how clueless most journalists are about living on a tight budget, so to do some research and because I was out of tamarind bars...
(mainly because of the tamarind bars), I dropped by the 99 Cent Only Store.
Much if not most of the food you'll find here is junk or junk adjacent, but there are healthy options. You can prepare some tasty, nutritious, filling and very cheap meals if:
You have access to one of these stores (preferably with a car so you don't have to haul groceries on a bus);
You're flexible about your menu (inventories are driven by odd lots and approaching expiration dates so you don't know what you'll find);
You have time to shop and to cook;
You have the facilities to cook and store lots of food;
You like beans.
And potatoes (rice works too)
,
Hot sauce is your friend.
It's not obvious from the picture but this is a pretty big can.
I don't want to oversell the virtues of these stores or understate the challenges of maintaining a healthy diet near the poverty line, but too many of the people driving the hunger debate are coming from a Whole Foods sensibility and they inevitably screw up the discussion no matter how good their intentions may be.
I don't have time to delve into this as deeply as I would like, but there's an interesting labor story developing here in LA. It pits union management against people who are normally very pro-labor.
Here's a slightly edited rant on the subject by Ken Levine.
What’s the point of having a union if it goes against the overwhelming wishes of its members? That’s exactly what happened last week when Los Angeles Actors Equity members voted over 2-1 to keep things status quo in the small theater (99 seats or fewer) LA scene; to not demand they be paid minimum wage per hour for all performances and rehearsals – and the New York board completely dismissed their vote and implemented it anyway. ... Why even conduct a vote if you completely ignore the results? Jesus! Elections in Iran are more legitimate.
My hope is that the LA branch breaks off from Actors Equity. Or files such a blizzard of lawsuits against the union that it completely strangles its ability to govern.
Here’s the issue: Small theaters make no money. For the most part they lose money. Everyone concerned does it for the love of theater. No one really gets paid – not actors, playwrights, directors, crews. The Whitefire Theatre in Studio City will be doing a one act play in June my partner, David Isaacs and I wrote. I’m also directing it. We’re making nothing. Not $9.00 an hour. Not $.09 an hour. But we’re thrilled to have the opportunity to see our work performed. We’re also employing eight actors. That means eight actors get to work on their craft, have a nice showcase, and perhaps get discovered.
And the evening will feature three one acts. Both the others also have casts of about eight. So do the math. Twenty-four actors, all the hours of rehearsal and performances – even at $9.00 an hour that adds up pretty quickly. Especially for a production where we have to buy our own props. If this ruling had already been in effect we simply would not do the production.
And this is what’s going to happen all over town. Producers will stop staging shows, small theaters will close, actors won’t work, and everybody loses (but Actors Equity).
LA actors understand this. They make their living in TV or films or commercials. And again, they voted 2-1 to not implement new restrictions. That's a mandate, folks.
...
But your union clearly doesn’t care. So what if they destroy the LA theater scene? As long as they maintain their control.
At your expense.
And by the way, I’m very pro-union. I’m a proud member of the WGA, DGA, AFTRA-SAG. I totally understand that without unions the studios and networks would pay us all less than a janitor makes in Cuba while raking in billions on the wings of our work. But no one is making money in small theaters.
So now it’s time for actors to take action. Your union is supposed to represent YOU. Actors Equity most definitely does NOT. Are you going to stand for that? Are you going to let a board with its own agenda dictate your career path? Send the message. Your vote COUNTS.
It’s bad enough actors face rejection every day, but to be rejected by its own union is, to me, intolerable.
This is consistent with something I've noticed about bicoastal musicians I've gotten a chance to talk with over the past few years. At least for small venues, everyone makes much more money back east, particularly in NYC. Audiences just seem to be willing to pay more.
In LA, performers tend to make their money in recorded media. Live performance plays more of a supporting role, developing craft, making connections, workshopping material. The proposed rule changes probably make sense from a New York vantage point, but most LA actors don't think they make sense here.
The Mars One habitat will be covered by a necessary layer of soil that provides shielding even against galactic cosmic rays. Sixteen feet (5 meters) of Martian soil provides the same protection as the Earth's atmosphere — equivalent to 1,000 grams per square cm(227.6 ounces per square inch) of shielding. The Mars One habitat can support a soil layer 36 feet (11 m) thick. If the settlers spend, on average, two hours per day outside the habitat, their individual exposure adds up to 22 mSv per year.
As mentioned before, two of the major issues in the Mars One involve the definition of "existing" technology and the way the project fails to account for technological unknowns and development costs. Case in point, the proposed Mars rover, which will have to greatly exceed any of its predecessors in functionality while remaining small enough to be lowered by sky crane (assuming that Mars One isn't planning on developing entirely new EDL [entry, descent and landing] technology).
Here are some relevant passages from the Mars One website [emphasis added].
Mars Landing Module: Mars One will secure the landing modules from one of the experienced suppliers in the world, for example Lockheed Martin. Similar landers will be equipped to perform different functions.
Carrying Life Support Units that generate energy, water and breathable air for the settlement.
Carrying Supply Unit with food, solar panels, spare parts and other components.
Carrying Living Units that are outfitted with deployable inflatable habitats.
Carrying Humans to the surface of Mars
Carrying Rovers to the surface of Mars
Rovers: Two rovers will be sent to Mars to set up the outpost before the humans arrive. One of them will explore the surface of Mars in search of the most suitable location for the settlement, transport of large hardware components, and the general assembly. Mars One’s rover supplier will determine the exact rover strategy; it is possible that instead of one large rover, multiple smaller rovers will be sent. For example, a main rover accompanied by a trailer system used for transporting the landing capsules.
You often encounter this kind of nonchalance about details in statements from Mars One, along with absolute confidence in the budget estimates that were based on those vague details.
The Mars One roadmap gives an idea of just how versatile the rover will have to be. Keep in mind, all of this has to be done autonomously before the first crew arrives.
One intelligent rover and one trailer will be launched. The rover can use the trailer to transport the landers to the outpost location. On Mars, the rover drives around the chosen region to find the best location for the settlement. An ideal location for the settlement needs to be far enough North for the soil to contain enough water, equatorial enough for maximum solar power, and flat enough to facilitate the construction of the settlement.
When the settlement location is determined, the rover will prepare the surface for the arrival of the cargo missions. It will also clear large areas where the solar panels will lie.
...
The six cargo units will land up to 10 km away from the outpost on Mars. The rover will pick up the first life support unit using the trailer, place the life support unit in the right place, and deploy the thin film solar panel of the life support unit. The rover will then be able to connect to the life support unit to recharge its batteries much faster than using only its own panels, which will allow it work much more efficiently.
The rover will pick up all the other cargo units and deploy the thin film solar panel of the second life support unit and the inflatable sections of the living units.
...
The rover will also deposit Martian soil on top of the inflatable sections of the habitat for radiation shielding.
We are talking about a lot of soil here (think five meters) and a lot of heavy lifting and a lot of precise work. Add to that concerns like dust and the need to be absolutely maintenance-free (if the rover breaks down, future launches can't proceed). To accomplish all of this will require a tremendous amount of engineering talent. Mars One claims this can be done quickly at bargain-basement prices.
NASA called for proposals for the rover's scientific instruments in April 2004,[80] and eight proposals were selected on December 14 of that year.[80] Testing and design of components also began in late 2004, including Aerojet's designing of a monopropellant engine with the ability to throttle from 15–100 percent thrust with a fixed propellant inlet pressure.[80]
By November 2008 most hardware and software development was complete, and testing continued.[81] At this point, cost overruns were approximately $400 million. In the attempts to meet the launch date, several instruments and a cache for samples were removed and other instruments and cameras were simplified to simplify testing and integration of the rover.[82][83] The next month, NASA delayed the launch to late 2011 because of inadequate testing time.[84][85][86] Eventually the costs for developing the rover did reach $2.47 billion, that for a rover that initially had been classified as a medium-cost mission with a maximum budget of $650 million, yet NASA still had to ask for an additional $82 million to meet the planned November launch.
In case you were wondering what a sky crane looked like.
This is one of the many reasons why aerospace people roll their eyes when Mars One CEO Bas Lansdorp starts talking about being able to carry out the project just using existing technology.
There’s no comfort in the statistics for missions to Mars. To date over 60% of the missions have failed. The scientists and engineers of these undertakings use phrases like “Six Minutes of Terror,” and “The Great Galactic Ghoul” to illustrate their experiences, evidence of the anxiety that’s evoked by sending a robotic spacecraft to Mars — even among those who have devoted their careers to the task. But mention sending a human mission to land on the Red Planet, with payloads several factors larger than an unmanned spacecraft and the trepidation among that same group grows even larger. Why?
Nobody knows how to do it.
Surprised? Most people are, says Rob Manning the Chief Engineer for the Mars Exploration Directorate and presently the only person who has led teams to land three robotic spacecraft successfully on the surface of Mars.
“It turns out that most people aren’t aware of this problem and very few have worried about the details of how you get something very heavy safely to the surface of Mars,” said Manning.
He believes many people immediately come to the conclusion that landing humans on Mars should be easy. After all, humans have landed successfully on the Moon and we can land our human-carrying vehicles from space to Earth. And since Mars falls between the Earth and the Moon in size, and also in the amount of atmosphere it has then the middle ground of Mars should be easy. “There’s the mindset that we should just be able to connect the dots in between,” said Manning.
But as of now, the dots will need to connect across a large abyss.
“We know what the problems are. I like to blame the god of war,” quipped Manning. “This planet is not friendly or conducive for landing.”
The real problem is the combination of Mars’ atmosphere and the size of spacecraft needed for human missions. So far, our robotic spacecraft have been small enough to enable at least some success in reaching the surface safely. But while the Apollo lunar lander weighed approximately 10 metric tons, a human mission to Mars will require three to six times that mass, given the restraints of staying on the planet for a year. Landing a payload that heavy on Mars is currently impossible, using our existing capabilities. “There’s too much atmosphere on Mars to land heavy vehicles like we do on the moon, using propulsive technology completely,” said Manning, “and there’s too little atmosphere to land like we do on Earth. So, it’s in this ugly, grey zone.”
But what about airbags, parachutes, or thrusters that have been used on the previous successful robotic Mars missions, or a lifting body vehicle similar to the space shuttle?
None of those will work, either on their own or in combination, to land payloads of one metric ton and beyond on Mars. This problem affects not only human missions to the Red Planet, but also larger robotic missions such as a sample return. “Unfortunately, that’s where we are,” said Manning. “Until we come up with a whole new trick, a whole new system, landing humans on Mars will be an ugly and scary proposition.”
If you're interested in aerospace, I'd recommend reading the entire article. It walks through all of the not-very-good options in detail.
Although the ethical and legal challenges facing Mars One are considerable, this venture will ultimately rise or fall on the technical and engineering elements. The stated aim of Mars One, according to their website, is to use “existing technologies available from proven suppliers.”1 This statement provides the first crucial difficulty. At each crucial phase of the mission—travel to Mars, landing, and establishing a permanent colony—the claim that of utilizing existing technology is unsustainable.
For example, at present the only existing operational human spaceflight vehicle is the Russian Soyuz capsule. Mars One states that the existing technology that will be used to traverse millions of kilometers from the Earth to Mars will instead be a variant of SpaceX’s Dragon capsule. To call the considerable research and development that this would require as “existing technology” is, at best, grossly oversimplifying the issue.
The Mars One project also provides no detail in respect of the development of reliable and effective life support systems and the problematic subject of dealing with human waste disposal. These are issues that will ultimately need to be solved for a successful mission to Mars, and there is significant research and development activity ongoing in this area.2 Such technology is, however, by no means “existing” without a significant amount of investment in research and development.
The picture is very much the same when considering the critical issue of landing the Mars One colonists on the Martian surface. Considered one of the most problematic aspects of human exploration, it is this aspect of the Mars One project where the notion of using existing technology is exposed as being dangerously misleading. The existing technology that has landed rovers on Mars is inadequate for landing humans.3 The Martian atmosphere poses considerable and serious challenges for landing a heavy payload onto the surface. The atmosphere varies considerably, making it extremely difficult to scale up existing technology used to land small rovers. Supersonic retropropulsion, which at present seems the most promising method of overcoming the obstacles posed by the variable Martian atmosphere, still requires expensive research and development.4 Again, this is not a problem unique to the Mars One project. It is, however, a fundamental obstacle to a 2023 mission with a projected budget of $6 billion.
Assuming, however, that the Mars One crew successfully makes it to the Martian surface, one aspect of space technology that remains untested, and makes the Mars One project fundamentally different from any previous space activity, is the technology required for the permanent settlement of Mars. Much has been made of in situ resource utilization (ISRU) technologies that will enable the colonists to live off the land. The much-publicized MIT feasibility study of Mars One casts significant doubt on the readiness of this technology, none of which has been deployed in practice.5 When challenged on this, the Mars One team responded by maintaining that the MIT study was based on ISS operations and therefore the study does not provide a valid comparison.6
Such assertions are, however, inconsistent with the stated aim of using existing technology. Either Mars One will utilize existing technology that has been tested in space on the ISS (in which case the MIT study is valid), or they will be looking to extrapolate new, untested methods of ISRU, which raises questions of reliability and cost in terms of money and time. In any event, the MIT study did not consider issues such as establishing a reliable power system and communications network, as well as the costly issue of spacesuit and habitat development. All these issues raise further questions about the technical feasibility of the entire venture.
I was checking my mail the other day and I saw this.
I don't want to wast too much time on the marketing ethics of people who pitch house-flipping seminars. They are both too easy to criticize and largely immune to criticism.
Still, this one phrase struck me as too perfect to let pass.
The implication is that success is solely a function of effort and (implicitly) belief. I suppose this has always been associated with get-rich-quick schemes, but the underlying idea has become disturbingly common in a number of places including many corporations where aspirational language has become the official newspeak.
For a case study of how this works in real life, I refer you to Duke Fightmaster.
I broke down and posted this College Humor video at the teaching site. Obviously, you can see the gag coming, but it's well sustained and besides, how often does math humor close in one a million hits?
