« Come hear my talk next Tuesday | Main | Sometimes you expose the holes »



I'me not certain how they got their estimates, they reference a paper by Poole, but it isn't in the bibliography. What you get for using Word. Simon Jackman for voting intentions in the US government using data pooled over time uses a latent variable method, essentially item response theory (IRT), and I assume they use this or something that is effectively the same.

The problem with it, is that you need items spread across the range of difficulty, otherwise results can be dominated by a small number of items. In this case given that only 3 nations have voted in favour of the US action on Cuba this makes it a very difficult item. So getting it "correct", unless there are items of similar difficulty, would virtually define the value of the latent variable, which is what the right axis represents. Some sort of sensitivity analysis needs to be done without these unusual items. It is quite probable that they don't fit the IRT model anyway.

Verify your Comment

Previewing your Comment

This is only a preview. Your comment has not yet been posted.

Your comment could not be posted. Error type:
Your comment has been posted. Post another comment

The letters and numbers you entered did not match the image. Please try again.

As a final step before posting your comment, enter the letters and numbers you see in the image below. This prevents automated programs from posting comments.

Having trouble reading this image? View an alternate.


Post a comment

Your Information

(Name is required. Email address will not be displayed with the comment.)


Link to Principal Analytics Prep

See our curriculum, instructors. Apply.
Marketing analytics and data visualization expert. Author and Speaker. Currently at Columbia. See my full bio.

Book Blog

Link to junkcharts

Graphics design by Amanda Lee

The Read

Good Books

Keep in Touch

follow me on Twitter