The article "Television's Value to Kids: It's All in How They Use It" (Seattle Times, July 6, 2005) described a study in which researchers analyzed standardized test results and television viewing habits of 1700 children. They found that children who averaged more than two hours of television viewing per day when they were younger than 3 tended to score lower on measures of reading ability and short term memory.
a. Is the study described an observational study or an experiment?
b. Is it reasonable to conclude that watching two or more hours of television is the cause of lower reading scores? Explain.