(economics) The apparently paradoxical observation that people's reported happiness varies directly with income both among and within nations, but over time happiness does not trend upward as income continues to grow.

The observation that the French suffer a relatively low incidence of coronary heart disease, despite having a diet relatively rich in saturated fats.

The observation that the association of two variables for one subset of a population may be similar to the association of those variables in another subset, but different from the association of the variables in the total population.

plural of grandfather paradox

The paradox of time travel in which inconsistencies emerge through changing the past.

plural of bootstrap paradox

A time travel paradox in which the consequences of an event in the future travel back in time and cause an event in the past or present, which in turn is among the causes of the first event, forming a causal loop in which each event is caused by the other.

(rare) The statistical and psychological observation that a person is prone to prefer Coca-Cola over Pepsi when they have labels, but prone to prefer Pepsi over Coca-Cola when they are unlabelled.

A paradox, related to probability, where the expected win for repeated play of a game is infinite, so it seems that a player should be willing to pay any price to take part.

(philosophy, logic) A paradox involving statements such as "this sentence is false", or "the following statement is true: the previous statement is false", which cannot be meaningfully regarded as either true or false.