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 10 times too much medication is disturbingly common. One study suggests this error occurs in 1 percent 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.