Comments for Andrew Coury                             Grade: Check+


    1. (a)  Excellent!

      (b)  You have the right idea, but note that the number of 
           crimes went down, and the population went up.  This means
           that the crime rate definitely decreased.

    4.  Exactly the right idea.

    5.  Yes -- Especially in a case like this where results would 
        probably depend on the subjective interpretation of subjects'
        responses to questions like "is your food tasting better now?"
        I think it is likely that the doctors who did the first study
        were swayed by their knowledge of who was getting the treatment.
        They might not even have been aware they were doing it if they
        wanted the treatment to "succeed."

    6.  Maybe, but I think it is somewhat more likely that something
        like this happened:  The patients knew the design of the study.
        So if they didn't feel improvement in the first half, they 
        may have assumed they were getting the placebo then.  In the 
        second half, then, there may have been a placebo effect since
        they assumed they were getting the treatment. 

    7.  Good -- exactly right.

    8.  You got it!

    9.  Good!

    10.  Excellent.

    11.  For part b, recall that the "boot camp" is totally voluntary.
         That alone makes this a non-randomized experiment.

    12.  Excellent.