26 Nonparametric Statistics for Social and Behavioral Sciences
be utilized for nonrespondents. Usually follow-up requests are made two
weeks after an initial request for participation. It is not unusual to conduct
two follow-up requests.
After the data are collected via mail and online surveys, they should be
screened for complete and useable responses. Inventories, questionnaires,
and opinionnaires should be examined and forms with many missing
values or forms that appear to have set responses should not be included.
Depending upon the statistical procedures to be used, the data may need
statistical screening as well. It is a good idea for researchers to number each
form so that it can be reviewed easily if a mistake is made when data are ...