▁data ▁on ▁the ▁conditions ▁of ▁the ▁target ▁group ▁before ▁the ▁inter vention ▁began ▁( B am berger ▁et ▁al ., ▁ 2 0 0 4 ). ▁Another ▁possible ▁cause ▁of ▁data ▁constraints ▁is ▁if ▁the ▁data ▁have ▁been ▁collected ▁by ▁program ▁staff ▁and ▁contain ▁system atic ▁reporting ▁bi ases ▁or ▁poor ▁record ▁keeping ▁standards ▁and ▁is ▁subsequently ▁of ▁little ▁use ▁( B am berger ▁et ▁al ., ▁ 2 0 0 4 ). ▁Another ▁source ▁of ▁data ▁constraints ▁may ▁result ▁if ▁the ▁target ▁group ▁are ▁difficult ▁to ▁reach ▁to ▁collect ▁data ▁from ▁- ▁for ▁example ▁hom eless ▁people , ▁drug ▁add ict s , ▁migr ant ▁workers , ▁et ▁c eter a ▁( B am berger ▁et ▁al ., ▁ 2 0 0 4 ). ▁Data ▁constraints ▁can ▁be ▁addressed ▁by ▁re construct ing ▁bas eline ▁data ▁from ▁secondary ▁data ▁or ▁through ▁the ▁use ▁of ▁multiple ▁methods . ▁Multiple ▁methods , ▁such ▁as ▁the ▁combination ▁of ▁qual itative ▁and ▁quant itative ▁data ▁can ▁increase ▁valid ity ▁through ▁tri ang ulation ▁and ▁save ▁time ▁and ▁money . ▁Additionally , ▁these ▁constraints ▁may ▁be ▁de alt ▁with ▁through ▁careful ▁planning ▁and ▁consult ation ▁with ▁program ▁st ake hold ers . ▁By ▁clearly ▁ident ifying ▁and ▁understanding ▁client ▁needs ▁ahead ▁of ▁the ▁evaluation , ▁costs ▁and ▁time ▁of ▁the ▁evalu ative ▁process ▁can ▁be ▁stream lined ▁and ▁reduced , ▁while ▁still ▁maintain ing ▁cred ibility . ▁ ▁All ▁in ▁all , ▁ ▁time , ▁mon et ary ▁and ▁data ▁constraints ▁can ▁have ▁negative ▁imp lications ▁on