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Estimating efficacy of the vaccine from 95 true infections

Gaurav writes: The 94.5% efficacy announcement is based on comparing 5 of 15k to 90 of 15k: On Sunday, an independent monitoring board broke the code to examine 95 infections that were recorded starting two weeks after volunteers’ second dose — and discovered all but five illnesses occurred in participants who got the placebo. Similar […]

What went wrong with the polls in 2020? Another example.

Shortly before the election the New York Times ran this article, “The One Pollster in America Who Is Sure Trump Is Going to Win,” featuring Robert Cahaly, who on election day forecast Biden to win 235 electoral votes. As you may have heard, Biden actually won 306. Our Economist model gave a final prediction of […]

You don’t need a retina specialist to know which way the wind blows

Jayakrishna Ambati writes: I am a retina specialist and vision scientist at the University of Virginia. I am writing to you with a question on Bayesian statistics. I am performing a meta analysis of 5 clinical studies. In addition to a random effects meta analysis model, I am running Bayesian meta analysis models using half […]

The rise and fall and rise of randomized controlled trials (RCTs) in international development

Gil Eyal sends along this fascinating paper coauthored with Luciana de Souza Leão, “The rise of randomized controlled trials (RCTs) in international development in historical perspective.” Here’s the story: Although the buzz around RCT evaluations dates from the 2000s, we show that what we are witnessing now is a second wave of RCTs, while a […]

No, I don’t believe etc etc., even though they did a bunch of robustness checks.

Dale Lehman writes: You may have noticed this article mentioned on Marginal Revolution, I [Lehman] don’t have access to the published piece, but here’s a working paper version. It might be worth your taking a look. It has all the usual culprits: forking paths, statistical significance as the filter, etc etc. As usual, it […]

How science and science communication really work: coronavirus edition

Now that the election’s over, we can return to our regular coronavirus coverage. Nothing new since last night, so I wanted to share a couple of posts from a few months ago that I think remain relevant: No, there is no “tension between getting it fast and getting it right”: On first hearing, this statement […]

The Pfizer-Biontech Vaccine May Be A Lot More Effective Than You Think?

Ian Fellows writes: I [Fellows] just wrote up a little Bayesian analysis that I thought you might be interested in. Specifically, everyone seems fixated on the 90% effectiveness lower bound reported for the Pfizer vaccine, but the true efficacy is likely closer to 97%. Please let me know if you see any errors. I’m basing […]

“In the world of educational technology, the future actually is what it used to be”

Following up on this post from Audrey Watters, Mark Palko writes: I [Palko] have been arguing for a while that the broad outlines of our concept of the future were mostly established in the late 19th/early 20th Centuries and put in its current form in the Postwar Period. Here are a few more data points […]

Lying with statistics

As Deb Nolan and I wrote in our book, Teaching Statistics: A Bag of Tricks, the most basic form of lying with statistics is simply to make up a number. We gave the example of Senator McCarthy’s proclaimed (but nonexistent) list of 205 Communists, but we have a more recent example: One of the supposed […]

Bayesian Workflow

Aki Vehtari, Daniel Simpson, Charles C. Margossian, Bob Carpenter, Yuling Yao, Paul-Christian Bürkner, Lauren Kennedy, Jonah Gabry, Martin Modrák, and I write: The Bayesian approach to data analysis provides a powerful way to handle uncertainty in all observations, model parameters, and model structure using probability theory. Probabilistic programming languages make it easier to specify and […]

My scheduled talks this week

Department of Biostatistics, Harvard University: Today, Tues 10 Nov 2020, 1pm Department of Marketing, Arison School of Business, Israel: Thurs 12 Nov 2020, 10am (US eastern time) St. Louis Chapter of the American Statistical Association: Thurs 5pm 2020, 5pm (US eastern time) The listed topic for the first two events is election forecasting and for […]

What happens to the median voter when the electoral median is at 52/48 rather than 50/50?

Here’s a political science research project for you. Joe Biden got about 52 or 53% of the two-party vote, which was enough for him to get a pretty close win in the electoral college. As we’ve discussed, 52-48 is a close win by historical or international standards but a reasonably big win in the context […]

Stop-and-frisk data

People sometimes ask us for the data from our article on stop-and-frisk policing, but for legal reasons these data cannot be shared. Other data are available, though. Sharad Goel writes: You might also check out stop-and-frisk data from Chicago and Seattle. And, if you’re interested in traffic stop data as well, see our Open Policing […]

What would would mean to really take seriously the idea that our forecast probabilities were too far from 50%?

Here’s something I’ve been chewing on that I’m still working through. Suppose our forecast in a certain state is that candidate X will win 0.52 of the two-party vote, with a forecast standard deviation of 0.02. Suppose also that the forecast has a normal distribution. (We’ve talked about the possible advantages of long-tailed forecasts, but […]

Comparing election outcomes to our forecast and to the previous election

by Andrew Gelman and Elliott Morris Now that we have almost all the votes from almost all the states, we can step back and answer two questions: 1. How far off were our predictions? 2. How did Joe Biden’s performance compare to Hillary Clinton’s four years earlier? How far off were our predictions? Here’s what […]

Here’s why rot13 text looks so cool.

To avoid spoilers, I posted some text in rot13: V yvxrq gung ovg arne gur ortvaavat jurer Qnavry Penvt gnyxrq nobhg tbvat gb gur raq bs gur envaobj jurer gurer vf gehgu, naq gura jnvgvat sbe gur riragf bs gur fgbel gb trg gurer. Guvf frrzf gb zr gb qrfpevor n ybg bs jung erfrnepu […]

Don’t kid yourself. The polls messed up—and that would be the case even if we’d forecasted Biden losing Florida and only barely winning the electoral college

To continue our post-voting, pre-vote-counting assessment (see also here and here), I want to separate two issues which can get conflated:

How the election might have looked in a world without polls

On the radio this morning it was all about how Biden’s in the lead but Trump outperformed the polls just about everywhere. What if there had been no trial-heat polls? Then maybe the reporting would be how Biden outperformed Clinton almost everywhere, but given all the problems with the economy it’s surprising Trump kept it […]

Post-election post

A favorite demonstration in statistics classes is to show a coin and ask what is the probability it comes up heads when flipped. Students will correctly reply 1/2. You then flip the coin high into the air, catch it, slap it on your wrist, look at it, and cover it up again with your hand. […]

Why it can be rational to vote

I think I can best do my civic duty by running this one every Election Day, just like Art Buchwald on Thanksgiving. . . .