Lake Wobegon effect

The Lake Wobegon effect designates either
 * the human tendency to overestimate one's achievements and capabilities in relation to others, or
 * the finding that in many educational tests a vast majority of participants achieves results above the norm.

It is named for the fictional town of Lake Wobegon from the radio series A Prairie Home Companion, where, according to the presenter, Garrison Keillor, "all the women are strong, all the men are good-looking, and all the children are above average."

Overconfidence
Surveying drivers, the Swedish researcher Ola Svenson found that 80% of respondents rated themselves in the top 30% of all drivers. Asking college students about their popularity, Zuckerman and Jost (2001) showed that most students judged themselves to be "more popular than average".

In a similar way, a large majority of people claim to be above average; this phenomenon has been observed among drivers, CEOs, stock market analysts, college students, police officers and state education officials, among others. Experiments and surveys have repeatedly shown that most people believe that they possess attributes that are better or more desirable than average. The term is also used to describe a perceived tendency to treat children as "special" in order to boost their self-esteem, even though the children may only be average or even underperforming.

One College Board survey asked 829,000 high school seniors to rate themselves in a number of ways. When asked to rate their own ability to "get along with others", fewer than one percent rated themselves as below average. Furthermore, sixty percent rated themselves in the top ten percent, and one-fourth of respondents rated themselves in the top one percent. Some have argued that more subjective traits like this may be more easily distorted.

The effect has been found repeatedly by many other studies for other traits, including fairness, virtuosity, luck, and investing ability, to name a few. It is similar and may be related to ingroup bias and wishful thinking. In contrast, the worse-than-average effect refers to a tendency to underestimate oneself in certain conditions, which may include self-handicapping behavior. It can be compared to the false consensus effect.

Distorted statistics
In 1987, John Cannell completed a study that reported the statistically impossible finding that all states claimed average student test scores above the national norm. The finding is generally admitted; the causes are disputed. One possible cause is teaching to the test.

Asymmetric distributions
In most situations, there is no reason to expect that in a statistical survey exactly half of the participants score above-average, and the other half below-average. It is possible and not at all uncommon that the score distribution is asymmetric.

As an extreme case, if one point in a series is low enough, all other points may be above average (Five students are asked to rate their looks on a scale of 1 to 10. Four say they rate their looks as a 9 and the last one says their looks rate as a 4. The mean of that series would be 8, making 80% of the students of above 'average' looks.) And if a series is binary, every non zero point is above average (Students take a simple exam, which is rated as either passing (with a score of 1) or failing (with a score of 0). Assuming that at least one student fails the test and at least one student passes the test, the mean will lie somewhere between 1 and 0 and thus every student that fails the test will be below average (scoring 0) and every student that passes will be above average (scoring 1).)

Such effects of an asymmetric distribution would not normally be called a "Lake Wobegon effect". A Lake Wobegon effect is not an asymmetry, but an upwards shift of a statistical distribution.