She randomized 50 workdays between a treatment group and a control group. For each day from the treatment group, she took bus A, and for each day from the control group, she took bus B. Each day, she timed the length of her drive. This is really interesting what she did. It's very important. She randomized the 50 workdays. It's important she did this instead of just kind of waking up in the morning and just deciding on her own which bus to take because humans are infamously bad at being random.