Michelle Del Rio, Juan Alvarez, Tania Mayorga, Salvador Dominguez, Christina Sobin
A comparison of arsenic exposure in young children and home water arsenic in two rural West Texas communities
BMC public health
screening blood units compatibility constitutes bernoulli series estimating number units needed screened represents classic waiting time problem may resolved using negative binomial distribution currently recommended method estimating number units screened n find required number compatible units r given probability p n rp coincides mean negative binomial distribution actual number units screened often underestimated current method cumulative distribution function negative binomial distribution provides probability success compatibility fnrp function number trials performed attempted crossmatches n probability success trial p number successes compatible units required r choosing threshold cumulative probability sufficiently high f 09 example provide confidence projected number units screened underestimated less often 10 time f 09 estimated number attempted crossmatches ranges 13 23 times many number calculated current method rule thumb approximately 16 times current estimated number provides similar estimate n 16rp waiting time underestimation reduced significantly using negative binomial distribution solution accompanied improved customer satisfaction