Suppose we have collected exams scores for a statistics exam. Students are randomly assigned to one of two groups. Group 1 was to learn all of the material via in-person lectures and materials. Group 2 was to learn all of the material via online videos and materials. Researchers are interested in testing against the null hypothesis that there is no difference in population mean exam scores between the two delivery methods. There are the summary statistics after collecting data. Note that the sample sizes differ, because some subjects did not follow instructions correctly and so they were not included in the analysis. x1= 71.2, x2= 62.5
s1= 10.82, s2= 13.61
n1= 41, n2= 55

Required:
Is this an experimental or observational study?