10.48 It is claimed that tensile-strength measurements for a 12 mm–diameter steel rod should, on the average, be at least 8 units (N/mm2) higher than the tensile-strength measurements for a 10 mm–

diameter steel rod. Independent samples of 50 measurements each for the two sizes of rods gave the following results:

Is the claim justified at the 5% significance level?

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10-mm Rod X =545 S = 24 12-mm Rod X2 555 $2 = 18