Quick Answer. An experimental variable is something that a scientist changes during the course of an experiment. It is distinguished from a controlled variable, which could theoretically change, but the scientists keep constant. Continue Reading.
While you were pregnant, your baby developed tooth buds, the foundation for baby teeth (also called milk teeth). Very rarely, a baby is born with a tooth or two, or grows a tooth in the first few weeks of life. But the vast majority of babies sprout their first tooth sometime between 4 and 7 months old.
The time when teething begins varies widely. Most babies are 4 to 7 months old when the first tooth appears, according to the American Academy of Pediatrics. Some little ones may have to wait until they reach 15 months of age. Watch your baby's lower gum when you suspect he is teething. His first tooth will most likely be one of the bottom front teeth.