I administered a test and wanted to know if the exam scores were influenced by watching videos. The participants were randomly entered into 2 arms. I have one control arm that did not watch videos, and the second arm being the group that did watch videos. I administered a pretest, had them watch the videos, and then take a post-test to the groups, acquiring their scores. After tallying them, I combined the two scores into a data set of scores with the pre-test data first and the post-test data afterward. I ran causalimpact in R on the set. Here are the results that I got.
Posterior tail-area probability p: 0.0111
Posterior prob. of a causal effect: 98.89%
I wanted to know if I implemented causal impact appropriately given that I combined both the pretest and posttest data into one set and split based upon when the pre-test data ended and the post-test data started. I also wanted to know if my assumption of causality would make sense in this instance.