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.
Most babies sprout their first tooth when they're between 4 and 7 months old. An early developer may get his first tooth as early as 3 months, while it may take a late bloomer until he's a year old or more. (In very rare cases, a baby's first tooth is already visible at birth.) Whenever your baby's first tooth makes its appearance, celebrate the milestone by taking pictures and noting the date in your child's baby book.