Why is random assignment of participants to groups an important aspect of a properly designed experiment?

a. If the participants are randomly assigned, the researcher can assume that the people in each of the groups are pretty similar.

b. By randomly assigning participants, the researcher knows that whatever is learned from the experiment will also be true for the population from which the participants were selected.

c. Random assignment keeps expectations from influencing the results of the experiment.

d. If participants are not randomly assigned, it is impossible to replicate the experiment.

e. Statistical analysis cannot be performed on an experiment if random assignment is not used.