15.36 Decay of polyester fabric in landfills. Here are the breaking strengths (in pounds) of strips of polyester fabric buried in the ground for several lengths of time:23 Time Breaking strength 2 weeks 118 126 126 120 129 4 weeks 130 120 114 126 128 8 weeks 122 136 128 146 140 16 weeks 124 98 110 140 110 Breaking strength is a good measure of the extent to which the fabric has decayed.

(a) Find the standard deviations of the 4 samples.

They do not meet our rule of thumb for applying ANOVA. In addition, the sample buried for 16 weeks contains an outlier. We will use the Kruskal-

Wallis test.

(b) Find the medians of the four samples. What are the hypotheses for the Kruskal-Wallis test, expressed in terms of medians?

(c) Carry out the test and report your conclusion.