Due to the many advantages of online surveys, many researchers are
taking advantage of this survey method. Although for many psychological instruments, previous
studies have shown that online and paper-and-pencil administration formats have
equivalent results, other studies have shown that some online surveys result in
different score distributions from those observed through paper-and-pencil
administration. In this study, we conducted surveys using Zung’s
self-report depression scale (SDS) to Japanese undergraduates both online and
through paper-and-pencil and examined whether there are differences between different
administration formats only in the scale’s mean structures and, if so, why the
difference occurs. Analysis results showed that
there was the difference only in mean structures. Results also implied that
the online administration format lowers item thresholds; this decrease would
cause the difference between the two formats’ mean structures. Finally, we think
about the future directions of this research; to examine whether similar
results would be seen in other scales, other countries, and other generations.