Simply Statistics A statistics blog by Rafa Irizarry, Roger Peng, and Jeff Leek

What is going on with math education in the US?

When colleagues with young children seeking information about schools ask me if I like the Massachusetts public school my children attend, my answer is always the same: “it’s great…except for math”. The fact is that in our household we supplement our kids’ math education with significant extra curricular work in order to ensure that they receive a math education comparable to what we received as children in the public system.

The latest results from the Program for International Student Assessment (PISA) results show that there is a general problem with math education in the US. Were it a country, Massachusetts would have been in second place in reading, sixth in science, but 20th in math, only ten points above the OECD average of 490. The US as a whole did not fair nearly as well as MA, and the same discrepancy between math and the other two subjects was present. In fact, among the top 30 performing countries ranked by their average of science and reading scores, the US has, by far, the largest discrepancy between math and the other two subjects tested by PISA. The difference of 27 was substantially greater than the second largest difference, which came from Finland at 17. Massachusetts had a difference of 28.

PISA 2015 Math minus average of science and reading

If we look at the trend of this difference since PISA was started 16 years ago, we see a disturbing progression. While science and reading have remained stable, math has declined. In 2000 the difference between the results in math and the other subjects was only 8.5. Furthermore, the US is not performing exceptionally well in any subject:

PISA 2015 Math versus average of science and reading

So what is going on? I’d love to read theories in the comment section. From my experience comparing my kids’ public schools now with those that I attended, I have one theory of my own. When I was a kid there was a math textbook. Even when a teacher was bad, it provided structure and an organized alternative for learning on your own. Today this approach is seen as being “algorithmic” and has fallen out of favor. “Project based learning” coupled with group activities have become popular replacements.

Project based learning is great in principle. But, speaking from experience, I can say it is very hard to come up with good projects, even for highly trained mathematical minds. And it is certainly much more time consuming for the instructor than following a textbook. Teachers don’t have more time now than they did 30 years ago so it is no surprise that this new more open approach leads to improvisation and mediocre lessons. A recent example of a pointless math project involved 5th graders picking a number and preparing a colorful poster showing “interesting” facts about this number. To make things worse in terms of math skills, students are often rewarded for effort, while correctness is secondary and often disregarded.

Regardless of the reason for the decline, given the trends we are seeing, we need to rethink the approach to math education. Math education may have had its problems in the past, but recent evidence suggests that the reforms of the past few decades seem to have only worsened the situation.

Note: To make these plots I download and read-in the data into R as described here.

Not So Standard Deviations Episode 27 - Special Guest Amelia McNamara

I had the pleasure of sitting down with Amelia McNamara, Visiting Assistant Professor of Statistical and Data Sciences at Smith College, to talk about data science, data journalism, visualization, the problems with R, and adult coloring books.

If you have questions you’d like Hilary and me to answer, you can send them to nssdeviations @ gmail.com or tweet us at @NSSDeviations.

Show notes:

Download the audio for this episode

Listen here:

Help choose the Leek group color palette

My research group just recently finish a paper where several different teams within the group worked on different analyses. If you are interested the paper describes the recount resource which includes processed versions of thousands of human RNA-seq data sets.

As part of this project each group had to contribute some plots to the paper. One thing that I noticed is that each person used their own color palette and theme when building the plots. When we wrote the paper this made it a little harder for the figures to all fit together - especially when different group members worked on a single panel of a multi-panel plot.

So I started thinking about setting up a Leek group theme for both base R and ggplot2 graphics. One of the first problems was that every group member had their own opinion about what the best color palette would be. So we are running a little competition to determine what the official Leek group color palette for plots will be in the future.

As part of that process, one of my awesome postdocs, Shannon Ellis, decided to collect some data on how people perceive different color palettes. The survey is here:

https://docs.google.com/forms/d/e/1FAIpQLSfHMXVsl7pxYGarGowJpwgDSf9lA2DfWJjjEON1fhuCh6KkRg/viewform?c=0&w=1

If you have a few minutes and have an opinion about colors (I know you do!) please consider participating in our little poll and helping to determine the future of Leek group plots!

Open letter to my lab: I am not "moving to Canada"

Dear Lab Members,

I know that the results of Tuesday’s election have many of you concerned about your future. You are not alone. I am concerned about my future as well. But I want you to know that I have no plans of going anywhere and I intend to dedicate as much time to our projects as I always have. Meeting, discussing ideas and putting them into practice with you is, by far, the best part of my job.

We are all concerned that if certain campaign promises are kept many of our fellow citizens may need our help. If this happens, then we will pause to do whatever we can to help. But I am currently cautiously optimistic that we will be able to continue focusing on helping society in the best way we know how: by doing scientific research.

This week Dr. Francis Collins assured us that there is strong bipartisan support for scientific research. As an example consider this op-ed in which Newt Gingrich advocates for doubling the NIH budget. There also seems to be wide consensus in this country that scientific research is highly beneficial to society and an understanding that to do the best research we need the best of the best no matter their gender, race, religion or country of origin. Nothing good comes from creative, intelligent, dedicated people leaving science.

I know there is much uncertainty but, as of now, there is nothing stopping us from continuing to work hard. My plan is to do just that and I hope you join me.

Not all forecasters got it wrong: Nate Silver does it again (again)

Four years ago we posted on Nate Silver’s, and other forecasters’, triumph over pundits. In contrast, after yesterday’s presidential election, results contradicted most polls and data-driven forecasters, several news articles came out wondering how this happened. It is important to point out that not all forecasters got it wrong. Statistically speaking, Nate Silver, once again, got it right.

To show this, below I include a plot showing the expected margin of victory for Clinton versus the actual results for the most competitive states provided by 538. It includes the uncertainty bands provided by 538 in this site (I eyeballed the band sizes to make the plot in R, so they are not exactly like 538’s).

538-2016-election

Note that if these are 95% confidence/credible intervals, 538 got 1 wrong. This is exactly what we expect since 15/16 is about 95%. Furthermore, judging by the plot here, 538 estimated the popular vote margin to be 3.6% with a confidence/credible interval of about 5%. This too was an accurate prediction since Clinton is going to win the popular vote by about 1% 0.5% (note this final result is in the margin of error of several traditional polls as well). Finally, when other forecasters were giving Trump between 14% and 0.1% chances of winning, 538 gave him about a 30% chance which is slightly more than what a team has when down 3-2 in the World Series. In contrast, in 2012 538 gave Romney only a 9% chance of winning. Also, remember, if in ten election cycles you call it for someone with a 70% chance, you should get it wrong 3 times. If you get it right every time then your 70% statement was wrong.

So how did 538 outperform all other forecasters? First, as far as I can tell they model the possibility of an overall bias, modeled as a random effect, that affects every state. This bias can be introduced by systematic lying to pollsters or under sampling some group. Note that this bias can’t be estimated from data from one election cycle but it’s variability can be estimated from historical data. 538 appear to estimate the standard error of this term to be about 2%. More details on this are included here. In 2016 we saw this bias and you can see it in the plot above (more points are above the line than below). The confidence bands account for this source of variabilty and furthermore their simulations account for the strong correlation you will see across states: the chance of seeing an upset in Pennsylvania, Wisconsin, and Michigan is not the product of an upset in each. In fact it’s much higher. Another advantage 538 had is that they somehow were able to predict a systematic, not random, bias against Trump. You can see this by comparing their adjusted data to the raw data (the adjustment favored Trump about 1.5 on average). We can clearly see this when comparing the 538 estimates to The Upshots’:

538-2016-election

The fact that 538 did so much better than other forecasters should remind us how hard it is to do data analysis in real life. Knowing math, statistics and programming is not enough. It requires experience and a deep understanding of the nuances related to the specific problem at hand. Nate Silver and the 538 team seem to understand this more than others.

Update: Jason Merkin points out (via Twitter) that 538 provides 80% credible intervals.