You believe that increasing illumination increases sped of productivity among piecework employees. Two groups are randomly selected from among the piecework employees at the Hawthorne Electric Company. Each participant is given 100 transistors to solder to the connecting relays. Group A works under normal plant lighting conditions whereas Group B experiences lighting that is increased by 50%. Is there a difference in time taken (in hours) by lighting condition? ___________ is the dependent variable in this problem. ___________ is the independent variable in this problem. ___________ is the appropriate statistical test to use for this