Risk, Heart and Head - リスク、感情と勘定

 Which operation is better?
#1 It will fail with prob of 60%, #2 It will succeed with prob of 40%

These operations will bring the same result, but it doesn't seem to.

If you take a cancer test, then the test is positive. The positive rate is 80% and the prob you have the cancer is also 80%, isn't it? Given about 5 people suffer from the cancer per 0.1 million people and the prob is 0.02%.

Speaking from the heart, a nuclear power plant is quite dangerous at the risk of having a high level of radiation. You might recall Hiroshima and Fukushima. However, speaking from the head, what percent is the prob that you suffer from a cancer and that you have a nuclear accident? It must be quite low. It should keep you much far away from there.

 ある２つの手術の結果として、どちらが望ましいか。
１）６０％の確率で失敗する。２）４０％の確率で成功する。

どちらも効果は同じだが、印象が違う。陽性率が８０％の癌検診を受け、陽性反応が出た。８０％で癌だろうか。発生頻度が人口10万あたり5.7人であれば、陽性反応が出たとして癌である確率は0.0228％。ずいぶん低い。

手術に限らず、原発の危険性を考える時、「感情」に訴えると、我々は非常な危険にさらされるが、「勘定」に訴えると、原発が事故り、放射線を受け、癌になるリスクはいくらだろうか。おそらく、非常に低いに違いない。