Lack of controlled experiment/ comparison:没考虑其他变量

The author unfairly assumes that it is ...that resulted in ... The causal relationship is convincing only if the author could demonstrate that all other factors that might affect ...remained constant during the same period.(pointing out that corresponding controlled experiment is needed, or explaining how the experiment should be conducted.)

Specifically, we need to know (the experiment result of one group of the subjects), Without appropriate comparison between A and B, the assumption that ...is unwarranted.