“试验者”的英语？

小儿从肩上抛球,抛至了天外的试验者手中就可记分.Child must throw ball overhand 3 feet to witnin arm's reach of tester.无因不良反应退出试验者.There was no exit of enrollees due to adverse reaction.这位试验者将20毫升的酸液吸入吸量管中.The experimenter sucked up 20 cc o...