# Analysis of some predictions about the 2018 EA Survey
## Introduction.
Some effective altruists made predictions about the 2018 EA Survey: a survey which aims to reach most people within the effective altruism movement. Here, I present the set up for the prediction making, the questions, and explain some judgement calls I made when judging the answers. Everything is written such that you can play along.
## Set up
For every question, try to come up with an interval such that you're 80% confident the answer lies in it. If you use a search engine, the surveys from previous years are fair game.
## Judgement call
In some cases, people didn't answer the question. For example, under the is.veg variable, you can have TRUE, FALSE, or NA: Not Available. If their number is respectively x, y and z, it might be a good first order approximation to estimate the actual proportion of vegetarians/vegans as x/(x+y).
However, I've decided to be extremely anal about it, and choose to define the actual proportion of people who define as vegan as x/(x+y+z). To do otherwise would be to replace questions. This doesn't make much of a difference in the case of plant eating, but it does in the identity politics questions. Curiously, doing so *raises* the average number of questions participants got right, but not by much.
The average accuracy is 55.12%, that is, the average participant got 13.22 out of 24 questions right. If it had been reached, a target credence of 80% would imply an average of 19.2 correct answers. In other words, in this limited domain, when these people say 80%, the thing happens 55% of the time. If they bet, they'd be replacing ~1:1 bets with 1:4 bets.