Georgie believes that a special juice will increase the productivity of his workers. He creates two groups, two workers per group. Both groups are assigned the same task, stapling a set of papers. Group A is given the special juice to drink while they work. Group B is not given the special juice. After an hour, Georgie counts how many stacks of papers each group has stapled. Group A stapled 1,320 stacks while Group B stapled 2,200 stacks. Georgie concluded that the juice was not effective in improving productivity. How would you improve Georgie's experimental design to produce a more valid conclusion?

Select one:
a. Georgie should use more than two people per group.
b. Georgie should also consider employee attendance as a variable.
c. Both groups should take the juice, just a different amount of it.
d. Georgie should not do this experiment as it has no practical implications.