2.10 Optional: Random allocation

This question is optional; e.g., if you need more practice, or you are studying for the exam.

(Answers are available in Sect.A.2)

For a small pilot study, Sam allocated $12$ students ( $6$ males and $6$ females) to one of two groups. In the Report associated with the study, Sam stated that the $12$ students were

...randomly allocated to one of two groups (Group A or Group B).

Different interventions were applied to each group. A reviewer, however, noted that all the subjects in Group A were male, and all the subjects in Group B were female.

Would this be a problem? Why?
Do you agree with Sam, that the subjects really were allocated to the groups at random? Explain your answer.