关于一个定义的解释，请求帮忙！

skysophie

Definitions.-An arrangement of v objects (called treatments) in b sets
6 E0 d5 d1 F: F: S(called blocks) will be called a pairwise balanced design of index unity and type
) k1 t6 h  N5 o  s% d(v; ki, k2, .. ., ki) if each block contains either k1, k2, .. ., or km treatments which
are all distinct (k, < v, k, $ kj), and every pair of distinct treatments occurs exactly
in one block of the design. If the number of blocks containing k, treatments is
+ R4 F) \+ E8 ib,, then clearly  b = A bi, v(v-1) = i biki(k -1)。。。

9 C! s1 v7 Q' q' w+ C# W谁能帮我解释一下，可以举个简单的例子。。谢谢！~
* U5 O. c0 O: S0 q# {  p1 x3 }

角凳

是告诉我们这是哪个领域的么？？