quantitative scoring method of totaling itemized scores

叠加 does not seem to be superposition, which is particularly applicable for waves with different phases (peaks, nodes, and troughs). My search suggests that it is arithmetic addition for the term asked.
http://www.51lunwen.com/details/lw200801131316547999-2.html

1.2.2模型评价于末次鼻腔致敏后30 min内，观察动物搔鼻动作，喷嚏、鼻溢液和觅食行为，以上各项指标均采用****叠加量化记分法****，总分大于5分表示模型成功.

　　1.2.3记分鼻痒：轻搔鼻1~2次为1分，剧烈抓挠鼻面不止3分，介于二者之间为2分. 喷嚏：1~3个为1分；4~10个为2分；11个以上为3分. 清涕：流至前鼻孔为1分；超出前鼻孔为2分；涕流满面为3分.