16.51 Decay of polyester fabric.
In Exercise 16.17 (page 16-13), the breaking strengths (in pounds) of strips of polyester fabric buried in the ground were considered for two time points. Breaking strength is a good measure of the extent to which the fabric has decayed. Here are the breaking strengths for several lengths of time.18
poly2
Time | Breaking strength | ||||
2 weeks | 118 | 126 | 126 | 120 | 129 |
4 weeks | 130 | 120 | 114 | 126 | 128 |
8 weeks | 122 | 136 | 128 | 146 | 131 |
16 weeks | 124 | 98 | 110 | 140 | 110 |
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16.51
(a) The standard deviations are 4.60, 6.54, 9.04, 16.09. (b) The medians are 126, 126, 131, 110. H0: The median breaking strength for all groups are the same. Ha: Some medians are higher in some groups than in others. (c) , . The data do not show median breaking strength differences across different times; there appears to be no decay.