\input zb-basic \input zb-matheduc \iteman{ZMATH 2007b.00487} \itemau{Malkevitch, Joseph} \itemti{Drugs and blocks.} \itemso{Consortium 2006, No. 91, 7-9 (2006).} \itemab Summary: The branch of mathematics that is concerned witn patterns in data -- statistics -- is critical for making sure that drugs and treatments are effective and safe. What is surprising is that one specialized tool that is used is also a part of combinatorics and geometry. What are block designs or, as they are perhaps more commonly known, BIBDs (Balanced Incomplete Block Design)? We start with a set of objects variously referred to as points or varieties (showing the statistical origins of the idea) denoted by $V$, as well as a collection $B$ of subsets of $V$, called blocks (or lines), all of which have the same number of elements $k$. We insist that every element of $V$ be contained in exactly $r$ blocks and that any pair of elements of $V$ lie in exactiy $\lambda$ blocks. The number of elements in $V$, $v$, and the number elements in $B$, $b$, as well as $k$, $r$, and $\lambda$ are called the parameters of the block design. The article presents some very simple examples of BIBDs that illustrate the roots of interest in this subject with geometry. \itemrv{~} \itemcc{M60 G90 K20 N70} \itemut{medicine; finite geometries; finite affine planes; finite projective planes; mathematical applications; pharmacy} \itemli{} \end