I decided to study the effect of lecture notes on test performance. My students choose to attend class in the day or the evening. I assigned my evening class to the experimental group (they get the...

I decided to study the effect of lecture notes on test performance.  My students choose to attend class in the day or the evening.  I assigned my evening class to the experimental group (they get the lecture notes), and my day session class to the control group (they did not get the lecture notes) of my study.  I treated both classes in the same manner (with the exception of lecture note distribution).  At the end of the semester, I measured test performance.  This study had __________ but did not have __________:

1. random assignment ; a manipulated independent variable


2. random selection ; an ABA design


3. a manipulated independent variable ; random assignment


4. an ABA design ; a case study.