1. In an experiment, participants are usually assigned to treatments ising a random assignment procedure. Why is random assigment used? 2. A reasearcher wants to know if brighter lights make factory...

1. In an experiment, participants are usually assigned to treatments ising a random assignment procedure. Why is random assigment used?

2. A reasearcher wants to know if brighter lights make factory workers more productive. Workers in a factory are randomly assigned to two groups. One group is moved to a new factory next door, where the factory lights are brighter. The other group stays behind in the old factory. The productivity if the two groups is comepared.
3. What is the independent variable(s)? What is the dependent variables(s)? What is the plausible confounding variable in this study?