The solid is not completely submerged in the water. Will this technique error increase, decrease, or have no effect on the reported density of the solid?

This technique error will increase the reported density of the solid.

Since the solid isn't completely submerged in the water, the volume will be reported as less than it actually is. Since volume is inversely proportional to density (if one goes up the other goes down), the density will increase and be reported as more than it actually is.