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2. (20 pt.] The data set (Concrete1.xlsx) contains the compressive strength, in thousands of pounds per square inch (psi), of 30 samples of concrete taken two and seven days after pouring. (a) At the 0.05 level of significance, is there evidence of a difference in the mean strengths at two days and at seven days? Show the work: 1) your hypotheses, il) test statistic, i) critical value, and iv) decision. (b) Find the p-value in (a) and interpret its meaning, (c) At the 0.05 level of significance, is there evidence that the mean strength is lower at two days than at seven days? Show the work: 1) your hypotheses, il) test statistic, lil) critical value, and I decision. (d) Find the p-value in (c) and make a decision 00 D N N 4 S 9 1 N 1 A B C 1 Sample Two Days Seven Days 1 2.830 3.505 3 2 3.295 3.430 4 3 2.710 3.670 5 4 2.855 3.355 B 5 2.980 3.985 7 6 3.065 3.630 8 7 3.765 4.570 9 8 3.265 3.700 10 9 3.170 3.660 11 10 2.895 3.250 12 11 2.630 2.850 13 12 2.830 3.340 14 13 2.935 3.630 15 14 3.115 3.675 16 15 2.985 3.475 17 16 3.135 3.605 18 17 2.750 3.250 19 18 3.205 3.540 20 19 3.000 4.005 21 20 3.035 3.595 22 21 1.635 2.275 23 22 2.270 3.910 24 23 2.895 2.915 25 24 2.845 4.530 26 25 2.205 2.280 27 3.590 3.915 28 3.080 3.140 29 28 3.335 3.580 30 29 3.800 4.070 31 30 2.680 3.805 32 33 N No ovo un 0 22 26 27

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