Question

The data in the Excel sheet labeled 'Concrete' represent the compressive ​strength, in thousands of pounds per square inch​ (psi), of 20 samples of concrete taken two and seven days after pouring.

At the 0.01 level of​ significance, is there evidence that the mean strength is lower at two days than at seven​ days?

What test will you use?

What is the p-value?

Reject Ho?

Is there evidence of a lower strength?

	Two days	Seven days
Sample
1	3.8	4.07
2	3.135	3.605
3	3.205	3.59
4	2.985	3.475
5	2.71	3.67
6	3.425	4.03
7	2.895	3.25
8	2.855	3.355
9	3.295	3.43
10	2.935	3.63
11	3.035	3.595
12	3.115	3.675
13	2.68	3.805
14	2.845	4.53
15	2.75	3.25
16	2.205	2.28
17	3.065	3.63
18	2.895	2.915
19	2.06	2.945
20	2.63	2.85

Answer 1

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