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Body-slam on the sister blog

John Ahlquist and Scott Gehlbach nail it.

Yes, I’ll help people for free but not like this!

I received the following (unsolicited) email: Dear Sir or Madam, My name is **; I am a graduate student, working on my thesis in **. A vital part of my research is performing a joint cluster analysis of attributional and relational data on **. I have tried to collaborate with the statisticians at ** and […]

And sometimes they don’t spam you at all

I received the following email: Dear Dr. Gelman, As a way of introduction, my name is . . . and I am very interested in studying in Columbia’s PhD statistics program. For the past 2 ½ years, I’ve worked as an analyst for . . . I am writing to communicate my interest in your […]

2 on chess

Is it really “often easier to win a rematch than to defend a championship”? The quoted bit above comes from Tyler Cowen, writing about the Anand/Carlsen world championship rematch. I’m still not used to the idea of a new world championship match every year but I guess why not? Anyway, here’s my question. Tyler Cowen […]

On deck this week

Mon: 2 on chess Tues: Yes, I’ll help people for free but not like this! Wed: I love it when I can respond to a question with a single link Thurs: Boo! Who’s afraid of availability bias? Fri: This is where they publish the stuff that’s can’t make it into Psychological Science Sat: Ray Could […]

Solution to the sample-allocation problem

See this recent post for background. Here’s the question: You are designing an experiment where you are estimating a linear dose-response pattern with a dose that x can take on the values 1, 2, 3, and the response is continuous. Suppose that there is no systematic error and that the measurement variance is proportional to x. You […]

Solution to the problem on the distribution of p-values

See this recent post for background. Here’s the question: It is sometimes said that the p-value is uniformly distributed if the null hypothesis is true. Give two different reasons why this statement is not in general true. The problem is with real examples, not just toy examples, so your reasons should not involve degenerate situations such as […]

Solution to the helicopter design problem

See yesterday’s post for background. Here’s the question: In the helicopter activity, pairs of students design paper ”helicopters” and compete to create the copter that takes longest to reach the ground when dropped from a fixed height. The two parameters of the helicopter, a and b, correspond to the length of certain cuts in the […]

Some questions from our Ph.D. statistics qualifying exam

In the in-class applied statistics qualifying exam, students had 4 hours to do 6 problems. Here were the 3 problems I submitted: In the helicopter activity, pairs of students design paper ”helicopters” and compete to create the copter that takes longest to reach the ground when dropped from a fixed height. The two parameters of the […]

Sailing between the Scylla of hyping of sexy research and the Charybdis of reflexive skepticism

Recently I had a disagreement with Larry Bartels which I think is worth sharing with you. Larry and I took opposite positions on the hot topic of science criticism. To put things in a positive way, Larry was writing about some interesting recent research which I then constructively criticized. To be more negative, Larry was […]