Will cash bonuses speed the return to work of unemployed people? A state department of labor notes that last year 68% of people who filed claims for unemployment insurance found a new job within 15 weeks. As an experiment, this year the state offers $500 to people filing unemployment claims if they find a job within 15 weeks. The percent who do so increases to 77%. What flaw in the design of this experiment makes it impossible to say if the bonus really caused the increase to 77%? O We do not know if the people filing unemployment claims are a representative sample of all unemployed people. There was no control group for comparison purposes. O There should have been another bonus level of $1000 to see if that produced a bigger increase. O There is no flaw in the design. O This is actually an observational study, not an experiment, and so cause-and-effect cannot be established