When conducting an experiment on time management, jamie assigns everyone who arrives before noon to the experimental group and everyone who arrives after 12 noon to the control group. in the context of experimental research methods, what is wrong with jamie's experiment?

The answer is "Jamie has not used true random assignment to conditions."

Random assignment alludes to the utilization of chance methods in psychology analyses to guarantee that every member has a similar chance to be relegated to any given gathering.  

Study members are randomly allocated to various groups, for example, the experimental gathering, or treatment gathering. Random assignment may include such strategies as flipping a coin, moving dice, or allotting arbitrary numbers to members.  

Note that random assignment varies from random selection.