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.
Count Blank/Nonblank Cells. This example shows you how to count the number of blank and nonblank cells in Excel. 1. The COUNTBLANK function counts the number of blank cells. 2. The COUNTA function counts the number of nonblank cells.