When all participants receive all treatment conditions, the study is susceptible to

When all participants receive all treatment conditions, the study is susceptible to Options: (a) Order effects (b) Carry over effects (c) Analysis of covariance (d) Both a & b ✅ Correct option: (d) Both a & b Explanation (200+ words): When all participants in an experiment receive all treatment conditions, the study design is known as a within-subjects or repeated-measures design. Although this design has advantages such as reduced variability and fewer participants, it is susceptible to order effects and carryover effects. Order effects occur when the sequence in which treatments are presented influences participants’ performance. For example, participants may improve simply due to practice or become tired due to fatigue. Carryover effects happen when the effect of one treatment persists and influences responses to subsequent treatments. These effects can distort results and threaten the internal validity of the study. Researchers often use counterbalancing or washout periods to minimize these effects. Since both order and carryover effects are relevant in such designs, option (d) is correct. Analysis of covariance is a statistical technique, not a threat. Hence, it cannot be the correct answer. 10 PPSC-Oriented Facts: 1. Repeated-measures design uses same participants. 2. Order effects affect performance. 3. Carryover effects influence later treatments. 4. Internal validity may be threatened. 5. Counterbalancing reduces bias. 6. Practice and fatigue cause order effects. 7. Washout periods control carryover. 8. Experimental design impacts results. 9. Research methodology topic. 10. Frequently asked in exams.