Final answer:
The incorrect statement is that Tuckman's theory of group development stages has been universally supported by empirical testing. Group development stages vary in duration and intensity, and effective teams undergo maturation, but Tuckman's stages are not empirically supported.
Step-by-step explanation:
The statement that is not true about group development is C. Tuckman's theory of group development stages has been strongly supported by empirical testing. While Bruce Tuckman's model of the stages of group development, including forming, storming, norming, and performing, is a well-regarded conceptual framework, it has not been universally supported by empirical research. Instead, group development can be far more fluid, without clear-cut stages that all groups uniformly experience.
It is accurate that all the stages of group development are not necessarily of the same duration (A) or intensity (B), as each group’s dynamics are unique. Furthermore, effective groups and teams do go through a maturation process (D), improving and evolving over time. It is also true that the storming stage can vary in length depending on several factors (E).