{"study":"Bolton et al. 1979","sample":"General psychology","control":"Random assignment","ni":10,"ri":0.68}
{"study":"Bryson 1974","sample":"College algebra","control":"CIAT pretest","ni":20,"ri":0.56}
{"study":"Centra 1977","sample":"General biology","control":"Final exam for prior semester of same course","ni":13,"ri":0.23}
{"study":"Centra 1977","sample":"General psychology","control":"Final exam for prior semester of same course","ni":22,"ri":0.64}
{"study":"Crooks & Smock 1974","sample":"General physics","control":"Math pretest","ni":28,"ri":0.49}
{"study":"Doyle & Crichton 1978","sample":"Introductory communications","control":"PSAT verbal score","ni":12,"ri":-0.04}
{"study":"Doyle & Whitely 1974","sample":"Beginning French","control":"Minnesota Scholastic Aptitude Test","ni":12,"ri":0.49}
{"study":"Elliott 1950","sample":"General chemistry","control":"College entrance exam scores","ni":36,"ri":0.33}
{"study":"Ellis & Rickard 1977","sample":"General psychology","control":"Random assignment","ni":19,"ri":0.58}
{"study":"Frey et al. 1975","sample":"Introductory calculus","control":"SAT math scores","ni":12,"ri":0.18}
{"study":"Greenwood et al. 1976","sample":"Analytic geometry and calculus","control":"Achievement pretest","ni":36,"ri":-0.11}
{"study":"Hoffman 1978","sample":"Introductory math","control":"SAT math scores","ni":75,"ri":0.27}
{"study":"McKeachie et al. 1971","sample":"General psychology","control":"Intelligence test scores","ni":33,"ri":0.26}
{"study":"Morsh et al. 1956","sample":"Aircraft mechanics","control":"Hydraulics pretest","ni":121,"ri":0.4}
{"study":"Remmers et al. 1949","sample":"General chemistry","control":"Orientation test scores","ni":37,"ri":0.49}
{"study":"Sullivan & Skanes 1974","sample":"First-year science","control":"Random assignment","ni":14,"ri":0.51}
{"study":"Sullivan & Skanes 1974","sample":"Introductory psychology","control":"Random assignment","ni":40,"ri":0.4}
{"study":"Sullivan & Skanes 1974","sample":"First-year math","control":"Random assignment","ni":16,"ri":0.34}
{"study":"Sullivan & Skanes 1974","sample":"First-year biology","control":"Random assignment","ni":14,"ri":0.42}
{"study":"Wherry 1952","sample":"Introductory psychology","control":"Ability scores","ni":20,"ri":0.16}