Author Archives: John Roe

“Spreadsheets of Power”

Here is a rather different take on economic modeling (including the kind that went into the Stern Review, presumably).

This article is about the use of mathematics (in the form of economic modeling) to distract and obfuscate – to shut down debate.  My hope in offering this course is that mathematics can also empower.

Probably a blog post or two in here somewhere!


The precautionary principle

A good topic for blog posts in our general theme area of “probability” for this week might be the precautionary principle.  This idea, which has legal force in some countries, has several forms: one of them is that “if a proposed action is suspected of causing a risk to the environment, then  those proposing the action need to demonstrate that it does not propose a risk; those opposing the action do not need to demonstrate that it does pose a risk.”

Here is a basic scientific paper on the principle


and a link to an important early consensus statement

Wingspread Statement

The precautionary principle is appealing, but there are some obvious problems with it, for instance: What counts as “demonstrated” absence of harm?  What if our choice is not between “risk” and “safety” but between two courses of action both of which are “risky” in different ways?

You could post about the application of these ideas, and its relation to more probabilistic methods of risk assessment, in any one of several contexts: GMO foods, vaccines, cell phones and brain cancer, climate change…


Blogging theme week 11

This week marks the beginning of the third and final blogging period.  The instructional team has not yet reviewed and fixed the grades for blogging period 2, but simply based on the number of posts it is clear that many of you will need to take advantage of the way the scoring system works to raise your blogging grades in this final period. We had a good discussion about blogging in class last Wednesday and the handout from that session is available here if you missed it.

For this week my suggested theme is “Probability in the Media”.   Find a media item (a news article, a YouTube clip, a web page, whatever) that uses probability in relation to an environmental theme, and analyze the ideas using the concepts that we have discussed in class (conditional probability, payoffs, expectations and so on).

Remember that, as always, the theme is only a suggestion.  You are welcome to post on any relevant topic, including one of the earlier suggested themes.  Here is a list of those:


Events schedule for week 11

Here is the schedule for the coming week

      • Monday 3/30,  2:30 – 3:20, Class Unit  3.5 (115 Osmond) – this will be a presentation about the Stern Review and how its methodology relates to the discussion in Unit 3.4
      • Monday 3/30,  4:00-5:00, Kaley Weinstein’s office hour and tech support (101 McAllister)
      • Tuesday 3/31 3:30-4:30, Sara Jamshidi’s office hours, 419 McAllister
      • Wednesday 4/1 2:30 – 3:20, Class – Case Study – Chris Uhl (Professor of Biology)
      • Thursday 4/2, 10:30 – 12:00, John Roe’s office hours, 204 McAllister
      • Friday 4/3, 2:30 – 3:20, Unit 3 Review (115 Osmond)
      • Monday 4/6, case study and second midterm exam (Monday-Wednesday)

Readings for  classes are available at

Scientific American article about probability and medicine

Here’s an article from Scientific American which gives a great review of the material we covered in class yesterday (Unit 3.3) in the context of medical testing.


The reference is
Gigerenzer, Gerd and others. April 2009. “Knowing Your Chances: What Health Stats Really Mean.” Scientific American,   44–53.

The notes for section 3.3 have some quotations from Gigerenzer’s book which is related to this article.

Blogging for week 10

I’m disappointed to see that there are no new posts on the blog this week.  I guess the most likely explanation is that most of the students are waiting until the third and final blogging period to try to raise your grade on the blogging component of the course.  The good news is that the blogging grade is the best score that you achieve in each of the three periods, so that there is still everything to aim for even if things have not gone well with your blogging so far.  On the flip side, the blog contributions make up 35 percent of your overall grade, meaning that quality blogging is vital if you want to succeed in this course.

This Wednesday in class we will run a workshop on blogging.  We’ll review the grading rubric, discuss a sample post, and look at ways to improve it.  Please also remember that you are welcome to discuss your blog posts in office hours at any time.  You may also revise any of your posts for blogging period 2 up until the deadline of Friday midnight; the final version is the one we will use for grading purposes.

As you know, you are free to write on any relevant subject in the blog.  I’ve listed past “theme” posts below.  For a new theme this week, I suggest that you might look at environmental justice.   If this phrase is not familiar, you can Google it, or ask yourself the following question: what one factor about a US community would you think best predicts whether or not it will be the site of a toxic waste dump?   The answer given in this 1987 report was a shocking one.  See also the twenty-year update given in 2007.

From the point of view of this course, the mathematical content of such a post could focus on the probabilistic or statistical techniques needed to show a correlation between the location of toxics facilities and the social/demographic profile of the neighborhood.  You can also ask what is the evidence for causation here (as opposed to correlation), and how relevant causation is to the justice question that these reports raise.

Here are the links to past weeks’ blogging themes.

Events schedule week 10

Here is the schedule for the tenth week of class.

  • Monday 3/23,  2:30 – 3:20, Class Unit  3.3 (115 Osmond)
  • Monday 3/23,  4:00-5:00, Kaley Weinstein’s office hour and tech support (101 McAllister)
  • Tuesday 3/24 3:30-4:30, Sara Jamshidi’s office hours, 419 McAllister
  • Wednesday 3/25 2:30 – 3:20, Class – Case Study –  Blogging with Mathematics (instructional team)
  • Thursday 3/26, 10:30 – 12:00, John Roe’s office hours, 204 McAllister
  • Friday 3/27, 2:30 – 3:20, Class Unit 3.4 (115 Osmond)
  • Friday 3/27, second blogging period ends.

Readings for  classes are available at

Regression to the mean

One topic we will address in Unit 3.3 is “regression to the mean”.  That is the statistical fact that if one member of a random series is extreme, the next is most likely going to be closer to the average.

The article below gives an interesting take on this in looking at the chances that the children of successful politicians have to grow up as successful politicians themselves.


Student groups on sustainability

Someone asked me after class yesterday whether I could point them to a list of student groups or clubs related to the theme of the class.

Asking around, I found that PSU’s Sustainability Institute maintains a list of such groups at

The groups range from ones with a very specific campus focused mission  to ones with a wider community or global mission.  If you are looking to follow up on the course experience, perhaps one of these will be the right opportunity.

I should mention also that towards the end of the semester, Susannah Barsom of Sustainability Institute will do one of our “case study” sessions to talk about other academic and non-academic opportunities to work on sustainability issues during your time at PSU.