A reading specialist in a large public school system believes that the more time students spend reading, the better they will do in school. She plans a middle school experiment in which an SRS of 30 eighth graders will be assigned four extra hours of reading per week, an SRS of 30 seventh graders will be assigned two extra hours of reading per week, and an SRS of 30 sixth graders with no extra assigned reading will be a control group. After one school year, the mean GPAs from each group will be compared. Is this a good experimental design?

(A) Yes

(B) No, because while this design may point out an association between reading and GPA, it cannot establish a cause-and-effect relationship.

(C) No, because without blinding, there is a strong chance of a placebo effect.

(D) No, because any conclusion would be flawed because of blocking bias.

(E) No, because grade level is a lurking variable which may well be confounded with the variables under consideration.