For Questions Below, Use the Following: a Researcher Predicts That

Short Answer

For questions below, use the following: A researcher predicts that training on the balance beam reduces reading errors among learning disabled youngsters. A random sample of 9 children was selected from the population of learning-disabled children from a large metropolitan school district. They were all given a reading test and their errors recorded. They were then trained on the balance beam for one year, and again their error scores on the reading test recorded. The data follows: $$\begin{array} { c c l } \text { Subject \#}& \text {Before } & \text { After } \\1 & 12 & 10 \\2 & 12 & 10 \\ 3 & 2 & 1 \\4 & 6 & 4 \\5 & 6 & 5 \\6 & 7 & 7 \\7 & 10 & 9 \\8 & 9 & 8 \\9 & 11 & 8\end{array}$$
-What is the major research error in the design of this experiment?