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. Author manuscript; available in PMC: 2012 Nov 1.
Published in final edited form as: Contemp Clin Trials. 2011 Aug 22;32(6):953–961. doi: 10.1016/j.cct.2011.08.004

Table 2.

Comparison of conditional allocation probabilities of the BUD and PBD (Three-treatment unbalanced allocation w1:w2:w3=1:2:2 Block size = 10)

i Randi Block urn design (BUD) Permuted block design (PBD)
Ni-1,1 Ni-1,2 Ni-1,3 ki-1 Pi1 Pi2
Ti&
Ni-1,1 Ni-1,2 Ni-1,3 Pi1 Pi2
Ti&
1 0.8290 0 0 0 0 2/10 4/10 3 0 0 0 2/10 4/10 3
2 0.4852 0 0 1 0 2/9 4/9 2 0 0 1 2/9 4/9 2
3 0.7767 0 1 1 0 2/8 3/8 3 0 1 1 2/8 3/8 3
4 0.0069 0 1 2 0 2/7 3/7 1 0 1 2 2/7 3/7 1
5 0.9145 1 1 2 0 1/6 3/6 3 1 1 2 1/6 3/6 3
6 0.5337 1 1 3 0 1/5 3/5 2 1 1 3 1/5 3/5 2
7 0.7652 1 2 3 1 2/9§ 4/9§ 3 1 2 3 1/4 2/4 3
8 0.1473 1 2 4 1 2/8 4/8 1 1 2 4 1/3 2/3 1
9 0.2346 2 2 4 1 1/7 4/7 2 2 2 4 0/2 2/2 2*
10 0.0684 2 3 4 1 1/6 3/6 1 2 3 4 0/1 1/1 2*
11 0.9372 3 3 4 1 0/5 3/5 3 2 4 4 2/10§ 4/10§ 3
12 0.8102 3 3 5 1 0/4 3/4 3 2 4 5 2/9 4/9 3
13 0.6827 3 3 6 1 0/3 3/3 2* 2 4 6 2/8 4/8 2
14 0.3290 3 4 6 2 1/7§ 4/7§ 2 2 5 6 2/7 3/7 2
15 0.6940 3 5 6 2 1/6 3/6 3 2 6 6 2/6 2/6 3
16 0.6481 3 5 7 2 1/5 3/5 2 2 6 7 2/5 2/5 2
17 0.9090 3 6 7 3 2/9§ 4/9§ 3 2 7 7 2/4 1/4 3
18 0.4940 3 6 8 3 2/8 4/8 2 2 7 8 2/3 1/3 1
19 0.3266 3 7 8 3 2/7 3/7 2 3 7 8 1/2 1/2 1
20 0.1690 3 8 8 3 2/6 2/6 1 4 7 8 0/1 1/1 2*
21 0.4618 4 8 8 4 2/10§ 4/10§ 2 4 8 8 2/10§ 4/10§ 2
22 0.4423 4 9 8 4 2/9 3/9 2 4 9 8 2/9 3/9 2
&

Ti = iif (Randi < Pi1, 1, iif (Randi < (Pi1 + Pi2), 2, 3))

*

: Deterministic assignment.

§

The active urn is updated by returning balls from the inactive urn.