Norbert wonders about the relationship between room temperature and feelings of belonging. He wonders if reducing room temperature by 1* would have an effect on feelings of belonging. To establish that the different levels of the independent variable are sufficiently different, he chooses to conduct a – by asking participants at the end of the study to report the perceived temperature in the room. He finds that the participants all report that the room is ‘comfortable.’ He wonders if 1* is simply not a large enough change to be noticed. To further his research, he runs a – by recruiting a small number of participants and measuring how many degrees the room temperature needs to be changed before it is noticeably less comfortable. These two techniques help to establish the – validity of the independent variable.