Could a confounding variable of an experiment be that the tests were conducted at different times?
Yes it could. For example, if the test for one condition was conducted very early in the morning and the test for the other condition conducted very late at night you could argue that any differences in effect were due to fatigue (e.g participants doing the test at night may be more tired than those doing it first thing). Types of confounding variable will vary depending on the experiment. If you are testing reaction time a confounding variable could be that the participants undergoing one condition are significantly older than participants in the other (e.g. teenagers and pensioners). Thus age should be distributed evenly between both conditions (unless age is an Independant Variable of course!). Practice/order effects are another confounding variable, which occur when participants need to complete the same or a similar task on more than one occasion. If test B is always performed after test A, it could be that participants perform better on task B simply because they got some practic
