Instructions:

1. Trial A (simple randomization)

• Flip a coin and assign Treatment A if heads and Treatment B if tails.

1. Trial B (blocked randomization)

• Use Table 10-6 (attached).
• Start in column 41, row 17, moving left to right and top to bottom.
• Using a block size of 4, if random number is:

-1 assign AABB

-2 assign ABAB

-3 assign ABBA

-4 assign BABA

-5 assign BBAA

-6 assign BAAB

-skip if 0, 7-9

1. Trial C (stratified randomization)

• Use Table 10-6 (attached).
• For clinic 1 start in column 35, row 6, moving left to right and top to bottom.
• For clinic 2 start in column 6, row 10, moving left to right and top to bottom.
• Use a variable block size alternating between block size of 4 and block size of 2.
• When using a block size of 4, if random number is:

-1 assign AABB

-2 assign ABAB

-3 assign ABBA

-4 assign BABA

-5 assign BBAA

-6 assign BAAB

-skip if 0, 7-9

• When using a block size of 2, if random number is even assign AB and if random number is odd assign BA.

Questions:

1. Why do or why don't the treatment groups deviate from the allocation ratio in each trial?

1. What is the minimum block size for a trial of 3 treatment groups stratified by 3 clinics, and an allocation ratio of 1:1:2?

100 Randomization and the mechanics of treatment masking Table 10-6 First 25 lines of page 17 of The Rand Corporation's 1 million random digits Column number Row number 5 10 15 20 25 30 35 4O 45 50 00397 56753 53158 71872 68153 09298 20961 49656 33407 95683 14328 44708 72952 27048 67887 28741 46752 88177 95894 40086 88534 87112 68614 83073 88794 96799 67588 75049 84603 83140 97347 87316 73087 77135 71883 98643 03808 08848 14133 60447 5 01366 72976 01868 51667 63279 60040 88264 79152 03474 61366 20523 21584 93712 83654 89761 90154 96345 37539 32556 74254 70603 97122 44978 78028 08943 13778 11080 34271 68266 85372 48410 94516 15427 75323 71685 70774 50342 33771 03678 42321 69788 41758 55004 30992 17402 63523 42328 87171 24751 15084 10 33884 83655 88345 69602 52606 57886 18034 03381 75796 35901 77480 28683 68324 66035 07223 14926 16128 13645 90370 31949 11057 98849 29499 21565 30786 83292 92392 37104 36899 49906 79368 43710 80365 88735 75275 21664 57965 19002 00301 12658 94385 01717 96191 50404 80166 93965 24688 27839 10812 31715 15 92127 42588 93307 80834 11317 26583 25769 98227 14887 58462 29148 68662 26872 72927 79021 51622 29521 33355 45701 45996 33782 93424 16530 96086 17329 74020 11501 46660 05583 22277 77653 55430 84644 00448 86828 58855 67451 95264 67386 82424 52611 60012 88620 72894 94716 22262 99813 69592 63464 33163 20 91857 47904 22209 78590 68615 52952 31441 41313 18550 72685 68825 04795 53971 14592 39634 23682 76630 02731 81481 86542 23727 54291 56045 61635 32186 90355 73416 63532 24340 18886 84832 30654 48543 18339 65024 91197 64624 74648 09660 27897 49771 11123 08732 49393 12911 72416 17834 18878 62754 85072 25 23727 56577 51257 83291 12329 16203 91681 68138 79959 43609 Source: Reference citation 387. Reprinted with permission of The Rand Corporation (New York: The Free Press, [955). Copyright 0 1955 and 1983 by The Rand Corporation