PBIB设计的约化

REDUCTION OF PBIB DESIGN

设是一个具有ｍ个结合类的ＰＢＩＢ设计，且它的多数λ＿１，λ＿２，．．．，λ＿ｍ中至少有两个是相等的。第二节中，给出了ＰＢＩＢ设计可以用遂次合并结合类来约化的充分必要条件。第三节给出了ＰＢＩＢ设计可以用同时合并结合类来约化的充分必要条件。最后，在第四节里我们研究了上述两种方法之间的关系。

Let be a PBIB design with m associate classes, and at leasttwo of its parameters λ_1,λ_2,...,λ_m be equal,In section 2, the necessary andsufficient condition for the PBI B design to be reducible by successivelycombining its associate ls given. In section 3,the necessary and suf ficientcondition for the PBI B design to be reducible by simultaneously combiningits associate classes is given. In section 4,we deal with the redtionship betweenthe above two methods.