Everyone makes mistakes, especially when it comes to entering numbers into a calculator or spreadsheet. It's not such a big deal if you're tracking how much you spend on pizza. But if you're administering drugs in a hospital, such a slip can be deadly. Now a report in the Journal of the Royal Society Interface shows how devices can be programmed to catch at least some mistakes on the spot. Dosing a patient with ten times too much medication is disturbingly common. One study suggests this error occurs in 1% of all hospital admissions. And though the person punching in the numbers is at fault, most drug-delivery devices don't help. In one machine, for example, mistakenly entering a number with two decimal points-like 1.2.3-might be read by the machine as 1.23, or as a 123. To prevent such wild guessing, scientists tested a system that immediately flags any input that's not a real number. According to their analysis, that safeguard alone could cut factor-of-10 errors in half. Charles Darwin once noted that "to kill an error is as good a service as establishing a new truth or fact." Even more so when killing the error keeps you from killing a patient.