▁in ▁which ▁only ▁single ▁indic ators ▁are ▁employed ▁for ▁each ▁of ▁the ▁variables ▁in ▁the ▁caus al ▁model . ▁That ▁is , ▁path ▁analysis ▁is ▁SE M ▁with ▁a ▁struct ural ▁model , ▁but ▁no ▁measurement ▁model . ▁Other ▁terms ▁used ▁to ▁refer ▁to ▁path ▁analysis ▁include ▁caus al ▁model ing , ▁analysis ▁of ▁cov ar iance ▁structures , ▁and ▁lat ent ▁variable ▁models . ▁ ▁Path ▁analysis ▁is ▁considered ▁by ▁J ude a ▁Pear l ▁to ▁be ▁a ▁direct ▁ancest or ▁to ▁the ▁techniques ▁of ▁C aus al ▁inference . ▁ ▁History ▁Path ▁analysis ▁was ▁developed ▁around ▁ 1 9 1 8 ▁by ▁gen etic ist ▁S ew all ▁Wright , ▁who ▁wrote ▁about ▁it ▁more ▁extens ively ▁in ▁the ▁ 1 9 2 0 s . ▁It ▁has ▁since ▁been ▁applied ▁to ▁a ▁vast ▁array ▁of ▁complex ▁model ing ▁areas , ▁including ▁bi ology , ▁psych ology , ▁soci ology , ▁and ▁econ omet rics . ▁ ▁Path ▁model ing ▁Typ ically , ▁path ▁models ▁consist ▁of ▁independent ▁and ▁dependent ▁variables ▁dep icted ▁graph ically ▁by ▁boxes ▁or ▁rect angles . ▁Vari ables ▁that ▁are ▁independent ▁variables , ▁and ▁not ▁dependent ▁variables , ▁are ▁called ▁ ▁' ex ogen ous '. ▁Graph ically , ▁these ▁ex ogen ous ▁variable ▁boxes ▁lie ▁at ▁outside ▁edges ▁of ▁the ▁model ▁and ▁have ▁only ▁single - head ed ▁ar rows ▁exit ing ▁from ▁them . ▁No ▁single - head ed ▁ar rows ▁point ▁at ▁ex ogen ous ▁variables . ▁Vari ables ▁that ▁are ▁sole ly