Van der Velden, van Loon, Benight, and Eckhardt (2012) investigated whether search and rescue workers called to Haiti following the 2010 earthquake suffered from mental health problems due to their high-stress work. To test this, they recorded the mental health of workers before and after search and rescue work in the region. In their study, the researchers reported a significant decline in mental health for depression, z = −1.977, p = .048, but not for anxiety, z = −0.816, p = .414.
(a) Were participants assigned to the same or different groups in this study?
(b) The researchers did not use a sign test to analyze these data. Thus, the nonparametric test computed in this study must be which test?