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 average age for the first tooth to erupt in infants is 6 months. This tooth is the bottom central incisor. Your child should have 20 primary (baby) teeth by 2 Â½ to 3 years of age. The first permanent molars, or 6 year molars, come in around the age of 6 and they erupt behind all of the primary teeth. Your child should lose their first tooth (lower central incisor) around the age of 6-7 years. The average age for a child to lose their last baby tooth is 12 years of age.