How does the Distance from the Camera to the Subject affect the Depth of Field?

How does the distance from the camera to the subject affect the Depth of Field?

 

We performed a study to determine how the distance from the camera to the subject affects the Depth of Field (DOF). As in all of our studies or experiments all of the parameters except for one are constant throughout the experiment.  The only parameter that will change in this study will be the distance from the camera to the subject. These are the parameters and a description of the study: