An Experimenter Conducts a Study in Which She Wants to Investigate

Multiple Choice

An experimenter conducts a study in which she wants to investigate the effects of eating chocolate on concentration.To do this she gives 20 people in an experimental condition a bar of chocolate and gives another 20 people in a control group nothing.However 4 of the people in the experiment withdraw because the dislike chocolate.Which of the following is a threat to internal validity?

A) Regression to the mean.
B) Practice effects.
C) Demand characteristics.
D) Mortality effects.
E) Experimenter bias.