This graph compares three filters to see how well they reduce the turbidity of the water samples.  The cheesecloth (red bars) successfully reduced the turbidity.  For the cheesecloth filters, the average turbidity was 12 JTUs before filtering and only 2 JTUs after filtering.  Gravel (yellow bars) also worked well for making the turbidity values smaller.  For the gravel filters, the average turbidity was 15 JTUs before filtering and 4 JTUs after filtering.  The alum (blue bars) was not as good at reducing the turbidity.  For the alum filters, the average turbidity was 7 JTUs before filtering and 6.5 JTUs after filtering.  

If I wanted a filter to reduce turbidity, I would use either a cheesecloth or gravel.  If I used both gravel and a cheesecloth, would it work even better at reducing turbidity?