What is the actual dressed size of a 2x4 stud?

The actual dressed size of a 2x4 stud is indeed 1-1/2 inches by 3-1/2 inches. This measurement reflects the size after the lumber has been planed down to remove roughness and to achieve a smooth finish.

Lumber dimensions are commonly referred to by their nominal size, which is what the piece of lumber is called before it is dressed. For example, a "2x4" refers to the nominal size, but due to the drying and planing processes the finished dimensions are smaller. Understanding this distinction is crucial for anyone involved in carpentry or construction, as it affects how materials are measured and ordered.

In contrast, the other sizes provided in the choices do not represent the actual dressed size of a 2x4 stud, but instead reflect theoretical or non-standard dimensions that are not used in carpentry practice for this standard framing lumber.