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.
The cell evaluates to an error value. The cell contains a text date with 2 digit years. The cell contains a number stored as text. The cell contains an inconsistent formula for a region. The cell contains a formula omitting a cell for a region. The cell which is unlocked contains a formula.