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.
Kids with no teeth by the age of 18 months should be taken to see a dentist, according to the American Academy of Pediatrics (AAP). Four to 15 months of age is the normal range for the appearance of the first tooth, and the other teeth usually follow in a regular schedule. Most children have four teeth by the time they are 11 months old, eight teeth at 15 months, 12 teeth at 19 months, 16 teeth at 23 months and 20 teeth at 27 months. Permanent teeth begin to appear around six years of age.