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
(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
8 Y- S. o  N+ o) {5 ]  F+ `are all distinct (k, < v, k, $ kj), and every pair of distinct treatments occurs exactly
- s4 T' K2 c8 Hin one block of the design. If the number of blocks containing k, treatments is
: E$ I* S: U* U" Hb,, then clearly  b = A bi, v(v-1) = i biki(k -1)。。。
1 ]- Z% h% ^# ?- n2 H, O
% @: H/ g+ C2 x. m4 [4 U2 }谁能帮我解释一下，可以举个简单的例子。。谢谢！~
- U! I3 E* R  b$ Y! q; b

角凳

是告诉我们这是哪个领域的么？？