Tuesday, November 10, 2009

Gay Marriage

I don't know if there is any issue with such a generational divide...

It currently appears that it's only a matter time before legalization.

Nate Silver projects when each state will legalize gay marriage via a regression model with the following variables:
1. The year in which (a gay marriage type) amendment was voted upon;
2. The percentage of adults in 2008 Gallup tracking surveys who said that religion was an important part of their daily lives;
3. The percentage of white evangelicals in the state.

He projects about half of states will legalize by 2014 and the rest by 2024. I personally think the status quo bias is a bit stronger than that and it'll take a little longer...

*Edit - Nate Sliver actually projects "the dates when the model predicts that each of the 50 states would vote against a marriage ban." The dates seem a bit more resonable now, but i still would be more conservative in the projections. Though maybe we've hit a tipping point?

Thursday, October 29, 2009

Childbirth and Evolution

From Half the Sky:

"One reason women die in childbirth has to do with anatomy, arising from two basic evolutionary trade-offs. The first is that once our ancient ancestors began to walk upright, too large a pelvis made upright walking and running inefficient and exhausting. A narrow pelvis permits fast running. That however makes childbirth exceedingly difficult. So the evolutionary adaptation is that women generally have medium-sized pelvises that permit moderately swift locomotion and allow them to survive childbirth - most of the time.

The other trade-off is head size. Beginning with our Cro-Magnon ancestors, human skull size expanded to accommodate more complex brains. Larger brains offer an evolutionary advantage once a child is born, but they increase the chance that a large-headed fetus will never emerge alive from the mother."


Thursday, October 8, 2009

Wednesday, October 7, 2009

Improving Self Reported BMI

Many epidemiological studies measure adiposity (obesity) through the surrogate BMI via self reported measures of height and weight. As I have mentioned before, there are many problems with this. But how can we improve on this while maintaining our level of accuracy and not using a direct measure requiring a more intensive doctor visit?

Two ideas to use along with BMI:
1. Waist size - pant size for men, dress size for women
2. Bench press - probably more reasonable for men. Could use max (weight you can bench press once), or weight you can bench press ten times.

Monday, March 16, 2009

Does the NCAA Selection Committee Use Regression Analysis?

The committees job is to pick and rank the 65 best college basketball teams (including those who won their conference tournaments). They want to choose the teams that are most likely to win games in the NCAA tournament. Now, regression analysis seems like a perfect tool for this type of dilemma, but does the selection committee use it?

Based on the slow involvement of statistics in other sports, my guess is no.

When college basketball experts talk about using "computers", I fear they are only talking comparing team's RPIs and Strength of Schedules via an eye test. The problem with these two measurements is that they are co-linear (a statistical way of saying too similar). All teams that have crappy RPIs are going to have crappy SOSs, like Penn State, since SOS is a part of RPI. Do we know how likely these measures predict success? I don't know, but there is a lot data from previous tournaments and it would be easy to determine. However, RPI and SOS would only explain a portion of the variability of the model. There are a lot of other variables that should be considered like record in the last 10 games, previous performance in tournaments, margin of victory, and potential injuries to key players. If these variables could help better predict a winning outcome (explain more of the variability in the model) then they should be included.

Yeah it's a human decision, and the committee does look at these variables and takes them into account. But there is a huge amount of bias in a purely human decision. It should be the human's decision to determine the variables in the regression analysis that makes the final decision. The committee may think that RPI is the most important variable and deserves the most weight. This may be true, but their assumption should at least be tested by regression.

During the selection show last night a committee member started to explain how they chose Arizona/Dayton over the other bubble teams. He emphasized that teams chosen were based on playing a competitive schedule throughout the year and winning quality games away from home. Of course Penn State had two huge road wins (MSU, Illinois) and Arizona didn't have any (and were 1-5 in their last six games). It's quite possible that the regression could have chosen the same 65 teams, but it would be interesting to see the analysis.

Thursday, February 26, 2009

Say Goodbye to Humanities?

Cool Article in the NYT on the decline seen in humanities:

It's not too surprising since the cost of education has dramatically increased, students have desired more return for their education. Now many don't have the luxury of studying less directly applicable areas. I also wonder if humanities degrees were artificially high in the 60s and 70s from all those hippies. haha

I agree in the article's point that Obama benefit the humanities field in multiple ways. He is a role model to many and he seems to greatly respect literature and philosophy. He also plans to make it more affordable to go to school through programs like the GI Bill and increased student aid. However, if the economy doesn't turn around, those points will probably be moot.

Wednesday, February 25, 2009

How Reliable is Health Advice?

Via the Health Blog:

Just 11% of more than 2,700 established heart recommendations are backed by high-quality testing, says a study in the current issue of JAMA.

The American College of Cardiology and American Heart Association jointly issue guidelines to doctors, WSJ explains. The ones thought to have the highest level of evidence are based on multiple randomized clinical trials. Those considered weakest are backed by expert opinion or case studies.

According to the JAMA paper there are three type of sources:
1. Sources based on multiple randomized clinical trials (high quality testing)
2. Sources based on a single randomized clinical trial or observational study (moderate)
3. Sources based on case studies, expert opinion - etc (poor)

As an epidemiologist, I will probably spend most of my time dealing with observational studies in the moderate category. While not "high quality", these are still important since many randomized control trials can not be conducted because of ethical, feasibility, and financial reasons. For example, we can't ethically conduct a randomized control trial on whether smoking causes lung cancer - since there is substantial evidence that we would inflecting harm in our control arm.

However, randomized clinical trials (RCTs) should be used whenever possible because they are removing many biases and confounding from the relationship of interest. A classic case of the benefit of RCTs is Hormone Replacement Theory (HRT) in women. The Nurses Health Study and others found a protective effect on mortality for HRT in several of their observational studies. Their evidence looked so convincing that hundreds of thousands of women went on the therapy. That was until randomized clinical trial results found that it can increase breast cancer and disease risk.

Getting back to the JAMA article, it's pretty scary when you think about. Heart Disease is America's biggest killer, and quite possibly the most widely studied disease. What this says is that there is a lot of work to do in the health field and that there will be a lot of reversals, ala HRT, of doctor opinion in future recommendations.

On a positive to note, I'm happy to say that we're headed in the right direction with this $1.1 billion dollar allocation to compartive effectiveness research in the stimulus package. Maybe Billy Beane had Mr. Obama's ear?

Monday, February 23, 2009

NYT: Index Funds Win Again

I am a big fan of index funds, owing shares in three of them. So I was happy to read this recent article:

Mr. Kritzman calculates that just to break even with the index fund, net of all expenses, the actively managed fund would have to outperform it by an average of 4.3 percentage points a year on a pre-expense basis. For the hedge fund, that margin would have to be 10 points a year.

The chances of finding such funds are next to zero, said Russell Wermers, a finance professor at the
University of Maryland. Consider the 452 domestic equity mutual funds in the Morningstar database that existed for the 20 years through January of this year. Morningstar reports that just 13 of those funds beat the Standard & Poor’s 500-stock index by at least four percentage points a year, on average, over that period. That’s less than 3 out of every 100 funds.

We'll see with these changing market conditions whether active mutual funds can continue their success of (almost always) swindling their clients.

Measuring Fat by MRI

A striking image that won a National Geographic Picture of Year award. The images are full body MRI shots of two women: 5'6" 250 lbs on the left, 5'5" 120 lbs on the right.

Looks like there is a lot of alteration in most areas of the body except for brain and maybe the ankle area. I wonder if pictures like these could be used for the fight against obesity?

Sunday, February 15, 2009

1979 vs. 2009

The New York Times and CBS has some nice new data out on a range of controversial issues. In this PDF, they compare the data to records they have from the late 1970s.

Here are a few I found notable:


Private Enterprise: 48%
Government - All Problems: 28%
Government - Emergencies: 12%
Don't know: 12%

Private Enterprise: 32% (-16%)
Government - All Problems: 49% (+21%)
Government - Emergencies: 10% (-2%)
Don't know: 9% (-3%)


Wrong: 62%
Not Wrong: 25%

Wrong: 41% (-21%)
Not Wrong: 54% (+29%)


Yes: 27%
No: 69%

Yes: 41% (+14%)
No: 52% (-17%)


U.S. Automakers - 46%
Foreign Automakers - 26%

U.S. Automakers - 29% (-17%)
Foreign Automakers - 55% (+29%)
Hat tip to this daily kos diary

Tuesday, February 3, 2009

Most Popular Big Cites

Another cool study by Pew Research Center:

I noticed, now that we're in the dead of winter, that most of the top cities are in warmer climates. I've never been to Denver (which seems to buck my observation), but maybe the air up there is just making them happy.

Tuesday, January 27, 2009

Teenage Sex Stats

From the Latest Well Article from Tara Parker-Pope:

Today, fewer than half of all high school students have had sex: 47.8 percent as of 2007, according to the National Youth Risk Behavior Survey, down from 54.1 percent in 1991.

A less recent report suggests that teenagers are also waiting longer to have sex than they did in the past. A 2002 report from the Department of Health and Human Services found that 30 percent of 15- to 17-year-old girls had experienced sex, down from 38 percent in 1995. During the same period, the percentage of sexually experienced boys in that age group dropped to 31 percent from 43 percent.

About 16 percent of teenagers say they have had oral sex but haven't yet had intercourse.

"I give presentations nationwide where I'm showing people that the virginity rate in college is higher than you think and the number of partners is lower than you think and hooking up more often than not does not mean intercourse," Dr. Bogle said. "But so many people think we're morally in trouble, in a downward spiral and teens are out of control. It's very difficult to convince people otherwise."

I wonder how these sex rates compare to the 1960s and 70s. Have rates significantly increased or are parents just hypocrites? While the given oral sex statistic is interesting, I wonder how many sexually active teens engage in oral sex. It sounds like the article is assuming that basically all of the sexually active teens engage in both.

Friday, January 23, 2009

Ryan Howard's Arbitration Case

I have been frequenting fangraphs.com recently, which is a great site for lots of cool baseball data and analysis. I recommend it for all the baseball stat nerds out there.

Recently Ryan Howard, the Phillies first base slugger, is in the news for having the biggest difference between arbitration figures submitted. Howard is asking for 18 million, while the Phillies submitted a figure of 14 million. Last year, in his first arbitration year, Howard took home a record 10 million for actually taking his case to arbitration judges and winning.

So in terms of arbitration, major league players have three arbitration years. Howard is in his 2nd year. According to Fangraphs, estimates on what players get are 40% of their free market value their 1st year, 60% their 2nd year, and 80% their 3rd year. So Howard should be getting about 60 percent of his free market value.

The Phillies with their 14 million dollar offer, think Howard is worth 19.6 million/year.
Howard with his 18 million dollar suggestion, thinks he's worth 25.2 million/year.

So basically Howard thinks he deserves the 2nd highest contract in league after ARod, who makes 27.5 million/year.

Looking at Fangraphs data, here are what the top Phillies were "worth" based on last year's production:

1. Chase Utley: 35.7 million
2. Jimmy Rollins: 23.1 million
3. Jayson Werth: 21.3 million
4. Cole Hamels: 20.6 million
5. Shane Victarino: 17.0 million
6. Ryan Howard: 14.1 million

The stats take into account his defense, replacement level (1b) performance, OPS (which went down .100 this year), and many other measures.

Howard has regressed the past three years, but considering his great 2nd half he will hopefully preform better next year. The Phils take that into account giving him a "19.6 million/year" deal (5.5 million more than he "made" last year).

Yes - Howard wants the 2nd "highest" salary in the major leagues, when he was potentially the 6th most valuable Philly last year.

It will be interesting to see what happens if this goes to arbitration. Do these arbitration judges think like MVP voters (Howard finished 2nd in NL MVP voting) or do they take into account statistics other than HR and RBI? I think either way Howard will lose his case.

A good point (by a fangraphs contributor) was made that needs to be considered.

He basically believes that Howard cannot be considered like a typical arbitration case, which would normally fall under the 40/60/80 rule. The problem with Howard is that the Phillies took awhile (age 26?) in calling him up (since they had Thome). Assuming the arbitration judges aren't ignorant like MVP voters, they probably rewarded Howard 10 million last year because he really should be in his 3rd year of arbitration (not his 2nd). I can understand that logic a bit more. If you make that assumption, Howard only thinks he's worth 21.6 million, which is a bit high but more understandable. In the above article, the fangraphs author used 2009 projections to calculate that Howard would be worth approximately 15 million (assuming he's in his "third" year of arb.)

So it could go either way I guess, but I still don't think he's worth the money.

Stat of the Week: Hospitials as Hotels

According to a paper from the National Bureau of Economic Research

"We also find that a one-standard-deviation increase in amenities raises a hospital's demand by 38.4% on average, whereas demand is substantially less responsive to clinical quality as measured by pneumonia mortality."

-It's interesting they used pneumonia mortality as a measure of clinical quality. I can only read the abstract, but I would assume that they adjusted for confounders and such like a good epidemiologist would do.

Media Attention and Risk Perception

From a Freaknomics interview of author Ben Sherwood:


Can a positive outcome to a crash like USAir 1549 change often unrealistic public perceptions of the fatality of plane crashes?


I doubt it. It’s incredibly safe to fly — your chances of dying on your next domestic flight are just one in 60 million — but many Americans are still petrified of air travel.

It’s no surprise: Plane crashes monopolize media coverage. Indeed, one MIT study found that airplane crash coverage on the front page of The New York Times was 60 times greater than reporting on HIV/AIDS per 1,000 deaths; 1,500 times greater than reporting on auto hazards; and 6,000 times greater than cancer.


Now, the key to this passage is they only looked at the front page. Still, it's very interesting and telling on why our perceived risks rarely match the actual risks.

Monday, January 12, 2009

Our (Potential) Future Surgeon General and Marijuana Legalization

Before I begin, I implore to you watch this Daily Show clip on Dr. Gupta. Aasif Mandvi does a great job. I hadn't laughed that hard in awhile. (start at minute 2 for the good stuff)

Anyway, Dr. Gupta recently wrote an article for Time Magazine entitled "Why I would vote No on Pot". I'm
pretty disappointed in this article by our (potential) future surgeon general. He brings to light both sides of the issue, but I don't think he argues his case very well.

So what did he bring up in the article (which leaves out other valid arguments for both sides):

positives of legalizing pot

- can help really sick people - those going through chemo, and those suffering from Alzheimer's
- 15 million people all ready use it, so wouldn't have to enforce law on them
- cut illegal drug trafficking and make communities safer

negatives of legalizing pot
- addiction
- affect short term memory
- impair cognitive ability
- lead to long term depression or anxiety
- can impair driving - cause accidents

First off I am disappointed by the lack of statistics. From this article I have no idea how severely pot affects short term memory, leads to long term depression, etc. A reasonable question would be, how do these negatives compare to alcohol? It seems that alcohol shares all of these negative consequences and is potentially worse in some cases. He also suggests outcomes that are rather subjective like depression, cognitive ability, etc. It is not nearly as clear cut as tobacco's relationship to lung cancer and other disease. I don't doubt his medical claims, but he should at least link to scientific/epidemiological studies supporting it.

So how authoritarian is Sanjay Gupta? Yes, it would be better medically if we banned alcohol and soda - but is it the right move for the country? There are reasonable reasons to keep marijuana illegal, but Dr. Gupta needs to bring a little more substance to his argument. Granted this was just a short article for Time Magazine, but adding links similar to Frank Rich's style at the New York Times would be refreshing.

One of my major reasons for reluctance of Gupta for Surgeon General is his lack of public health training or experience. If this is the way he would describe a public health epidemic in the future as surgeon general, consider me unimpressed.

Looking further at the Marijuana issue as a whole:

Gallup polling has explored the legalization of Marijuana question for years, and while support is still on Dr. Gupta's side the margin is eroding.

When asked if medical marijuana should be legalized, support jumps into the 70 percent range. Dr. Gupta points out that 11 states have all ready decriminalized marijuana for medical use. I honestly believe that polling (on legalization of both medical and recreational) would change if people were more informed on this subject.

For example, there is a very valid economic argument that would play well in today's economic situation.

Jeffery Miron an economist from Harvard conservatively estimates that the US could receive 14 billion dollars a year from the legalization of marijuana. "...the government would save $7.7 billion a year if it didn't have to spend money policing and prosecuting marijuana activity. Then, if the feds taxed marijuana at a rate comparable to cigarettes and booze, another $6.2 billion would come rolling in."

It will be interesting to see if any "change" is made on this issue with the Obama administration, considering it's the "#1 Idea" proposed on their site change.org.