Answer to Question 1
The interrupted time-series design involves a single group that is observed multiple times over the course of the study. The replicated design includes more than one group, so researchers can make comparisons of changes over time across groups. In addition, in the replicated design, the treatment can be applied to different groups at different times, increasing our confidence that the threats to internal validity like history, maturation, testing, or statistical regression (regression to the mean).
Answer to Question 2
a. internet research can ease the setup requirements for the experimenter who does not have to be in the lab at specific times to set up and take down research apparatus and materials
b. internet research does not require scheduling research when both the researcher and the participant are available; it can be done at the convenience of the participant
c. data collection is automated, so there are unlikely to be transcription or recording errors
d. the range of participants can be extended beyond the students on a researcher's campus