Editing Hand formula (section)

== Articulation of the rule ==
Hand stated:

{{quote|[T]he owner's duty, as in other similar situations, to provide against resulting injuries is a function of three variables: (1) The probability that she will break away; (2) the gravity of the resulting injury, if she does; (3) the burden of adequate precautions.}}

This relationship has been formalized by the [[law and economics]] school as such: an act is in breach of the [[duty of care]] if:

:<math>PL>B</math>

where ''B'' is the cost (burden) of taking precautions, and ''P'' is the probability of loss (''L'').  ''L'' is the gravity of loss.  The product of P x L must be a greater amount than B to create a duty of due care for the defendant.