As I said before, I don't think these variables will have much impact on our sample results. Although it was said that it rained on one of the days, by looking at the survey reports of past students I found that they also experienced the same thing. So the point I want to make is very interesting, that if a variable keeps happening then it can no longer be called a variable. Just like rain, if the students who took samples in previous years usually encountered at least one rainy days, the results of the samples they took should be the same as ours, and the results obtained after analysis are fair