Which among the following are the source of threat to external validity?
A. Sample characteristics
B. Novelty/uniqueness of stimulus
C. Improper manipulation of I.V.
D. Lack of motivation on the part of the participants
E. Reactivity of the assessments
Choose the correct answer from the options given below:
1
A, B and D only
2
B, D and E only
3
C, D and E only
4
A, B and E only