orthonormal comments on Participation in the LW Community Associated with Less Bias - Less Wrong

31 Post author: Unnamed 09 December 2012 12:15PM

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Comment author: wgd 10 December 2012 04:46:15AM *  3 points [-]

Could someone explain the reasoning behind answer A being the correct choice in Question 4? My analysis was to assume that, since 30 migraines a year is still pretty terrible (for the same reason that the difference in utility between 0 and 1 migraines per year is larger than the difference between 10 and 11), I should treat the question as asking "Which option offers more migraines avoided per unit money?"

Option A: $350 / 70 migraines avoided = $5 per migraine avoided
Option B: $100 / 50 migraines avoided = $2 per migraine avoided

And when I did the numbers in my head I thought it was obvious that the answer should be B. What exactly am I missing that led the upper tiers of LWers to select option A?

Comment author: orthonormal 10 December 2012 05:46:49AM 12 points [-]

You're answering the wrong question. "Which of these fixes more migraines per dollar" is a fast and frugal heuristic, but it doesn't answer the question of which you should purchase.

(If the first three wheels of your new car cost $10 each, but the fourth cost $100, you'd still want to shell out for the fourth, even though it gives you less wheel per dollar.)

In this case, the question you should be asking is, "is it worth another $250 a year to prevent another 20 migraines?", which is overwhelmingly worth it at even a lower-class time-money tradeoff rate. (The inability to do anything for several hours costs them more than $12.50 in outcomes- not to mention the agony.)