A researcher is conducting an experiment comparing three treatment conditions. If the researcher uses a between-subjects design, there will be score(s) for each participant but if a within-subjects design is used there will be score(s) for each participant.

1, 3

Explanation:

Between-subjects also called between-groups study design refers to when different individuals/participants in the experiment test each of the conditions/treatment(independent variable) allowing only person to be exposed to a single treatment/condituon while a within-subject design allows all participants to test all conditions so that one person tests all conditions or treatments. This is why there would be one result for each person under between-subject design and three in the other.