STATISTICAL EVALUATION OF CUTANEOUS IRRITANTS 823 After randomizing the assignment of each run to each position on each subject's back (i.e., each block), as well as the order of application of the patches, the experimental design was prepared and is shown in Fig. 6. Block 1 211 411 212 312 311 112 111 412 Subject 1 I Replicate 1 Block 2 422 321 421 221 222 121 322 122 Sub.i ect 2 Block 3 Block 4 212 311 111 312 112 411 211'412 Subject 3 I 121 122 322 421 321 221 222 422 Subiect 4 Replicate II Block 5 Block 6 211 212 412 111 311 411 312 112 Subject 5 Subiect 6 I . Replicate Ill Key to Identification of Runs: First digit (A): 1 = 0.5% 2 = 1% 3 = 2% 4 = 4% Second " (B): 1 = regular patch 2 = pressure patch Third " (C): 1 = 2 hours 2 = 24 hours 221 421 422 321 322 122 121 222 The procedure for this experiment was analogous to that used previously with the exception that the scoring system was changed for convenience. Since it had been established to the authors' satisfaction that readings to the nearest 0.25 score unit could be made, the scores for this experiment were recoded before analysis as shown below: Original Score New Score Original Score New Score 0.00 1 2.25 10 0.25 2 2.50 11 0.50 3 2.75 12 0.75 4 3.00 13 1.00 5 3.25 14 1.25 6 3.50 15 1.50 7 3.75 16 1.75 8 4.00 17 2.O0 9 Figure 6. Experimental design

824 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS ß ' I ß .