bankárkerekítés

Bankárkerekítés, also known as banker's rounding or engineer's rounding, is a method of rounding numbers that is often used in financial and scientific contexts. Unlike the more commonly taught round-half-up method, which rounds .5 up to the next whole number, banker's rounding rounds .5 to the nearest even number. For example, if rounding to the nearest integer, 2.5 would round to 2, and 3.5 would round to 4.

This rounding method aims to reduce bias in rounding over a large set of numbers. When rounding .5 always up, there's a tendency for the overall sum of rounded numbers to be slightly higher than the sum of the original numbers. Banker's rounding mitigates this by rounding halves in both directions (down to an even number and up to an even number), theoretically balancing out the cumulative rounding error.

The method is employed in many computer systems and programming languages by default for floating-point arithmetic. Its widespread use stems from its statistical properties, making it a preferred choice when accuracy and minimizing systematic bias are important considerations. While it may seem counterintuitive at first compared to traditional rounding, its objective is to provide a more neutral and statistically sound approach to approximating numbers.

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