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.
Starting at around 3 months of age, infants begin to show outward signs that baby teeth are coming. They produce more saliva and will put their fingers in their mouths. This drooling can go on for several weeks before you'll see a tooth. Infants typically get their first tooth between ages 5 and 12 months. The bottom incisors emerge first, followed by the top incisors. Usually around 2 years of age, a toddler has a full set of teeth, explains Dr. Edward Kulich of New York, NY.