For each of the following scenarios, call out the potential biases in the proposed experiment. Do your best to try to discover not only the bias, but the initial design. There is plenty of room for interpretation here, so make sure to state what assumptions you're making.

1. You're testing advertising emails for a bathing suit company and you test one version of the email in February and the other in May.
2. You open a clinic to treat anxiety and find that the people who visit show a higher rate of anxiety than the general population.
3. You launch a new ad billboard based campaign and see an increase in website visits in the first week.
4. You launch a loyalty program but see no change in visits in the first week.