Can the president of the united states remove his signature from a law after he signed it?

no they can not "unsign" it but they can The President may sign the bill at any time after its deliverance. If it sits unsigned for more than the 10-day period, it becomes law regardless of his signature or not. Normally, it is known if enough members will vote to override the bill two-thirds is needed

this null effect is caused by a weak manipulation and ineffective internal validity. in a scientific study, as the one dr. morimoto is trying to perfom, internal validity refers to the confidence placed in the cause-effect relationship and to how well an experiment is done and able to eliminate confounding variables.