Consider the following case: A researcher would like to know if highlighting textbook aids students to score better on exams. She randomly selects one-half of the students in introductory class and instructs them to highlight their textbooks as they read. The other students are instructed to do NO highlighting as they read.
1) Suppose that the researcher rejected the null hypothesis and concluded that there was a significant difference due to highlighting.
2) Can research demonstrate statistical significance, yet have no real practical value?
3) Could two groups have a difference that looked important, yet not be statistically different from one another? That is, could the difference between two groups appear to have practical value, yet not achieve statistical significance?