	Total unit response rate^c	Cases used in this study^d
Spring 2009 treatments (sample size)^b
Mail response (681)	53.2	351
Web response 1 (676)	50.2	281
Web response 2 (678)	64.5	387
Sum of web responses		668
Fall 2009 treatments (sample size)
Mail response (683)	43.9	299
Web response 1 (487)	42.5	194
Web response 2 (589)	38.2	209
Web response 3 (586)	21.2	115
Web response 4 (669)	20.5	126
Sum of web responses		644