Survival Bias – Sunday Surgical Scrub – 30 October 2016

sss-survival-bias

“Hi, I’m Bill. I’m a birth survivor.” -Bill Maher

 

TASK AT HAND: This week I’m thinking about survival bias, also known as survivorship bias. Survival bias is a logic error that produces false conclusions by looking at a person who achieved an outcome and overlooking those that did not, despite both having similar characteristics. Simply put, the “survivor” is used as a model to extrapolate from, only because they survived the event, despite the fact that many similar individuals exist for comparison that did not survive the event.

Let me use a couple of examples to illustrate the point. Usain Bolt, the Jamaican sprinter, is heralded as the fastest human ever timed. He is the first man to hold both the 100 and 200 meter records. He is an amazing sprinter, a charismatic character, and a fantastic entertainer. Many have tried to ascertain how he is able to run so fast. Bolt usually states common athletic creeds such as “belief in yourself” and “training hard”. Survival bias enters here because Usain Bolt is the fastest human in the history of mankind not because he trains hard and believes in himself, but despite this.

How many athletes believe in themselves and train hard? How many fall short? Too many to count. Many times athletes are asked how they achieve greatness and they usually provide the same predictable answers. The reason is, because they don’t know. They trained hard like everyone else but they, for some reason, were able to produce superlative results. Now, in no way do I diminish these feats. I celebrate them! But, you have to be careful in their extrapolation to your life.

Another example. Many want to be the next Steve Jobs and create a behemoth success like Apple. Steve Jobs dropped out of college and started a business. Do you think this was the reason? How many others have dropped out of school and started business that failed? Too many too count. Steve Jobs was the “survivor” of this event and succeeded not because he dropped out of school, but in spite of this.

There are numerous examples of survival bias in a myriad of disciplines so one needs to be aware of this erroneous process of reasoning. Survivorship bias leads to overly optimistic and simplified beliefs because only successful survivors are used while the many similar failures are ignored. Most of the time, the failures have very similar attributes and no significant relationship is evident.

This important because one needs to understand that successful groups – most of the time – do not have any special property. This does not diminish or lessen their achievement. But, when you are trying to reproduce some of these behaviors, consider both successful and failed examples. The role of timing, coincidence, and serendipity will become apparent.

How does this help you? Personally, it serves to balance my emotional reaction to events. I know I’m never as good as my best day. But, I’m also not as terrible as my worse day – and I don’t beat myself up over it. I survive each day, despite how factors beyond my control play out, and I remain focused on what I have defined as important.

MEDICINE & MACULA: A couple of weeks ago I described our technique for retinal embolectomy. This technique was recently published in Retinal Cases & Brief Reports. Retinal embolectomy involves the removal of emobli from the retinal vasculature in selective cases of arterial occlusions.

embolectomy1-copy

embolectomy2-copy

Check out the publication here.

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GRATIS: “Science is the search for truth, that is the effort to understand the world: it involves the rejection of bias, of dogma, of revelation, but not the rejection of morality.” -Linus Pauling

My best to you,

David Almeida

david@davidalmeidamd.com

2 Comments, RSS

  1. ana sanka October 30, 2016 @ 10:37 am

    As usual, your article is very well done and very well conceived.
    But you know why I admire you the most? Not only for your capacity but also for your humbleness and sincerity. From you, anybody can learn good things.
    May God bless you for ever my dear doctor.

    Best regards
    Ana

    • David Almeida October 30, 2016 @ 5:53 pm

      Thanks for the kind words Ana! And thanks for your interest. Best wishes!

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