25. \"Yes, cellphones and laptops do affect students' grades, and no, students can't multitask as well as they say they can.\" This sentence refers to a study in which one professor taught two sections of an upperlevel cognitive psychology course. Students were allowed to use electronic devices for half of the lectures and not allowed to use them for the other half, with students in the two sections receiving opposite instructions. At the end of the semester, grades on the allowed/ not allowed portions of the nal exam were compared. We are testing to see if students perform better when they are not distracted by electronic devices during class. Using ,ul for mean grade on material when devices are not allowed and p2 for mean grade on material when devices are allowed, the hypotheses are Ho ! M1 = #2 HCl 2 #1 > #2 Suppose we have created a randomization distribution from our sample. Two possible differences in sample means are shown. AIE152=2.8 32:3152:57 (a) Which sample result, A or B, will be closer to the center of the randomization distribution? (b) Which sample result, A or B, will be farther out in the tail of the randomization distribution? (c) Which sample result, A or B, will provide the stronger evidence against H0 and in support of H\"? (d) Explain in the context of lead contamination what it means to \"provide evidence against H0 and in support of Ha.\