Years ago I worked on a live TV show that allowed viewers to call and ask questions to hosts. It was a small local TV station but the show was some what popular. We wanted to know what variables affected how many calls there are per show and we manually tracked a bunch of data points and one of them was the weather. Once enough data was collected it was very clear for our show the weather had a big impact, when we had beautiful weather we had less calls but when the weather was horrible we had a lot more calls. In hindsight it was obvious that when it rains people will stay home and watch TV.

Another fun thing this data collecting showed me was subjective bias of certain managers. One of them was sure that a certain hosts were getting much less calls than the others during the show but the data showed that besides one "star" all the hosts have about the same amount of calls even though it "felt" like they got less.