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
  u7 b2 F6 y6 e(called blocks) will be called a pairwise balanced design of index unity and type
/ g* k  Y3 o3 U) `# k) l: W. S) X(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
  k$ ~1 o) X& n6 Q. i" Hin one block of the design. If the number of blocks containing k, treatments is
5 B: X& m& \2 U7 C5 @8 ub,, then clearly  b = A bi, v(v-1) = i biki(k -1)。。。
, a+ I7 o, Z3 B5 v& T: `
( q. k: C! h2 |# C# C谁能帮我解释一下，可以举个简单的例子。。谢谢！~

角凳

是告诉我们这是哪个领域的么？？