A more thorough explanation:

The Hand Formula is a legal test used to determine whether someone's conduct has created an unreasonable risk of harm. It was first introduced by Judge Learned Hand in a court case called United States v. Carroll Towing Co. in 1947.

According to the Hand Formula, a person is considered negligent if the burden of taking precautions against harm is outweighed by the probable gravity of the harm multiplied by the probability that the harm will occur. In simpler terms, if the cost of preventing harm is less than the potential harm itself, then the person is considered negligent.

For example, imagine a store owner who fails to put up a "wet floor" sign after mopping the floor. If a customer slips and falls, the store owner may be considered negligent under the Hand Formula. The cost of putting up a sign is low, but the potential harm of a customer slipping and injuring themselves is high.

Another example could be a driver who chooses to text while driving. The potential harm of causing a car accident is high, and the probability of an accident occurring is also high when distracted driving is involved. The burden of preventing harm, in this case, is simply putting down the phone and focusing on the road, which is much lower than the potential harm caused by an accident.