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Unformatted text preview: I 1078 n
129
129 mean
107.6
123.6 Ha: Y  X > 10
. The pvalue is essentially zero, so at any level of s
1.3
2.0 significance, we reject H0. The data overwhelmingly suggest that the mean tensile strength of the 1078 grade exceeds
2
the mean of the 1064 grade by more than 10 kg/mm .
b. A 95% confidence interval for Y  X will provide information on precision and reliability. The confidence interval is given
by . W e are 95% confident that the mean tensile strength of all 1078 gra de wire rods exceeds the mean tensile strength of the 1064 grade
2
wire rods by 15.59 to 16.41 kg/mm . 10. The data is summarized in the table.
a. The hypotheses are
H0: 1  2 = 5
The test statistic is versus Steel
1=High Purity
2=Commercial Ha: 1  2 > 5
. The pvalue is n
32
38 1.2
1.1 mean
65.6
59.8 P(2.89 < Z) = 1  .9981 = .0019. At the = .001 level of significance, we retain H0. The data do not provide sufficient
evidence at the 0.1% level of significance that the mean toughness of the high purity steel exceeds the mean for the
commercial grade by more than 5.
b. 13. If we set = mean deflection for the steel beams and = mean deflection for the beams made wi...
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 Spring '04
 Chung
 Standard Error

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