TABLE 2.

Coding of contrasts used to compare the effectiveness of the letters versions

Type of contrast	Comparison	Letters versions
		Version 1 (control)	Version 2	Version 3	Version 4	Version 5
Difference contrasts	V1 vs. V2	−1	1	0	0	0
	V1 and V2 vs. V3	−1	−1	2	0	0
	V1 and V2 and V3 vs. V4	−1	−1	−1	3	0
	V1 and V2 and V3 and V4 vs. V5	−1	−1	−1	−1	4
Simple contrasts (sensitivity analysis, see results in Appendix A)	V1 vs. V2	−1	1	0	0	0
	V1 vs. V3	−1	0	1	0	0
	V1 vs. V4	−1	0	0	1	0
	V1 vs. V5	−1	0	0	0	1
Repeated contrasts (sensitivity analysis, see results in Appendix A)	V1 vs. V2	−1	1	0	0	0
	V2 vs. V3	0	−1	1	0	0
	V3 vs. V4	0	0	−1	1	0
	V4 vs. V5	0	0	0	−1	1