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 2 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 2 or more hours of television is the cause of lower reading scores? Explain.