What statistical test was used in Nelson et al., (2010)?

Read Nelson, J. A. P., Young, B. J., Young, E. J., & Cox, G. (2010). Using teacher-written praise notes to promote a positive environment in a middle school. Preventing School Failure, 54(2), 119-125. 


1. What statistical test was used in Nelson et al., (2010)?
2. Did the authors use the correct statistical test? In other words, what was their rationale for using this test. For example, were the variables discrete or continuous and was the test appropriate for this type of data?)
3. What was the research question? How did the statistical test address and answer the research question?
4. How did the authors interpret the results of this study?