Also our common sense approach to risk is very unreliable. And who would not think it wise to bet on red in roulette if black had just come up ten times in a row. Some perceptions are quite irrational. For example I know mothers who when taking on a new au pair are very frightened that they will run off with the child if there has been even one such case reported. If I hear that a cyclist I know has been injured I am much more cautious than normal although my risk remains the same.
Statistics have little impact on such risk assessments.
A major error in personal risk assessment probably relates to our inability to make sound judgments when the amount of information is limited. For example, a little while ago there was a suggestion in the United States that a game called 'Dungeons and Dragons' was risky since it might lead to teenage suicide. The evidence in support of this claim was that twenty-eight teenagers who regularly played the game had committed suicide. But the average suicide rate for teenagers nationwide in the United States is about one in ten thousand. How often have we heard that so and so's father smoked thirty a day until the age of eighty without a day's illness.