Opinion| Selection bias model

Hatem Sadek
4 Min Read

I did not mean the headline to be difficult or ambiguous, but in fact, the “selection bias model” is an approach to thinking that concerns every individual. 

It is an accurate scientific outcome as there are events that have contributed to changing thinking methods and the logic of analysis. One of those events is a story that took place during World War II. 

At the time, British aircraft launched daily raids on Berlin to destroy the infrastructure of Nazi Germany. However, those air attacks incurred heavy losses for the British air force as a result of the strength of German air defences, which could ultimately lead to a humiliating defeat for the British Crown. 

Therefore, the leaders of the British Air Force decided to confront their losses and to identify their causes. But because their capabilities were limited at the time, and due to the scant scientific capabilities that were unable to identify weak areas that needed reinforcement in aircraft, they had to make a guess using logical inference.

They observed the following: the aircraft that returned were heavily hit by bullets in the wings and mid-plane, and to a lesser extent in the rear wing, while the pilot’s cabin and tail were almost untouched.

Consequently, they reached an important conclusion: the wings and the middle of the plane should be strengthened, as these are the places that seem easy to hit. Based on that conclusion, the reinforcement was made for the new aircraft, and engineers awaited the results. Despite that, no change has occurred. Most of the planes are still crashing, and a few are returning.

Here the army decided to seek the help of scientists outside of specialisation. Thus, the leaders of the British army chose the scientist Abraham Wald, an Austrian mathematician who fled Vienna because of the war. 

This scientist told them that they used an inverse logic in explaining the events, as the planes that returned, which were hit by shells in the wings and the middle, were the ones that endured the strikes and did not fall. Meanwhile, the planes that did not return were the planes that were hit in the pilot’s cabin or the tail, indicating that both cabin and tail are really the fragile places, which need strengthening.

The experiment confirmed the validity of his idea, and the percentage of surviving aircraft increased at a very large rate. So the principle was applied to the rest of the army’s weapons. 

Later, this became a reason to change patterns of thinking. This story established a model later called “selection bias”, which means that the analysis of information may be subject to a selective process based on inaccurate data, and this leads to incorrect results.

I believe that this model can be applied by every person to their life, and can be used to re-read many events and situations that the individual goes through. This will help them find out the compatibility and validity of the decisions they took with the requirements of those circumstances and events.

Dr Hatem Sadek, Professor at Helwan University

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