When did the Renaissance spread to northern Europe?

Explanation:

this slowed or prevented the spread of the renaissance ideas in the earlier years of the renaissance. however, when the hundred years' war ended in the mid-(15th )century it allowed the ideas of the Italian renaissance from the 14th century to extend north and west to other parts of Europe

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.