The American Optometric Association suggests that children should have their first regular eye exam at six months of age. Another vision exam should take place when a child is around two or three years of age when their vision undergoes its most rapid development and vision correction is most effective.
The ISNUMBER function is a quick, easy way to check if a cell contains a number. Our example used the IF function to illustrate how ISNUMBER can be used. If you haven't used IF in a formula before, you can read our lesson on the IF function here.
A human cell containing 22 autosomes and either an X or Y chromosome is a sperm cell. According to Genetics Home Reference, all female egg cells contain an X chromosome along with their 22 autosomes. This arrangement means that males determine the sex of the offspring during the egg's fertilization.