I am trying to add the text `Unknown` to a column if the cell is blank and if there is a value or text in the cell, then to leave it. Everything I have tried adds the text if blank, but it also writes over cells that had values already.

```
Column E
 Graduate
 Undergraduate
 (BLANK)
 Community

```

I have tried:

```
= IF (E2 <> "", E2, "Uknown")
= IF(ISBLANK(E2),"Uknown", E2)
= IF (NOT(ISBLANK(E2)), E2, "Unknown")

```

I messed up the cell values, but instead of adding `Unknown` it is appending zeroes.