The necessary assumptions are to get the sample for random sampling and ensure they are normal.
b. The standard deviation is known hence we have to make use of the z distribution.
42.08 - 40 / (3.39 /√26)
= 2.08 / 0.6648
= 3.129
≈3.13
p value
p(Z > 3.13)
= 0.0008770
8.7e-4
d. Z critical value = 2.81
42.08 +- 2.81 * 3.39/√26
= 42.08 +- 2.81*0.6648
= 42.08 - 1.868, 42.08 + 1.868
= 40.212 ,43.948
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