Blank cell on spreadsheet affecting chart, HELP!

I am creating a spreadshhet from a satifaction survey. When the person does not fill the survey out completely and I leave the cell blank, it appears in the graph as if I had entered 0%. How do I get blank cells to not affect my chart/graph??

you need to replace the blank cells with #N/A which will not be plotted

Awesome! Thanks for your help and quick response!!