A researcher is curious about the effect of sleep on students' test performances. He chooses 60 students and gives each two tests: one given after two hours' sleep and one after eight hours' sleep. The test the researcher should use would be:A) T-test for the differences in two means assuming equal variances) T-Test for the differences in two means assuming unequal variances) Paired t-test) F test for the differences in variances) Any of the above