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
2 P* P* N2 O3 P0 W% `+ h: S" T(called blocks) will be called a pairwise balanced design of index unity and type
(v; ki, k2, .. ., ki) if each block contains either k1, k2, .. ., or km treatments which
, J" e6 K( x- T7 ]  S3 u3 R. jare 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
b,, then clearly  b = A bi, v(v-1) = i biki(k -1)。。。
- ]/ u9 ?1 L5 S- ]+ G1 ~$ b
( z+ R, V5 f( x6 R" q) B9 }谁能帮我解释一下，可以举个简单的例子。。谢谢！~
8 M4 u. t  Z5 n" [% D

角凳

是告诉我们这是哪个领域的么？？