Suppose that a researcher is interested in whether having class at night causes students to learn more or less, compared to having class in the morning. One semester, the researcher teaches one section of a course in the morning and another section of the course at night. The researcher teaches the sections in the same way, with the same textbook, the same lectures, and the same assignments. Results for the final exam indicate that the students who signed up for and completed the morning section had a higher mean final exam score than students who signed up for and completed the night section, with a p-value of p<0.05 for a test of the null hypothesis that these mean final exam scores equaled each other. Is this sufficient evidence to conclude, at least among these students for this semester and this course, that having class at night caused students to learn less than having class in the morning?

Group of answer choices

A. Yes, because the p-value is less than p=0.05

B. No, because the students who signed up for and completed the morning section might have been different from the students who signed up for and completed the evening section, even before the course started