3.10. A product developer is investigating the tensile strength of a new synthetic fiber that will be used to make cloth for men’s shirts. Strength is usually affected by the percentage of cotton used in the blend of materials for the fiber. The engineer conducts a completely randomized experiment with five levels of cotton content and replicates the experiment five times. The data are shown in the following table.

(a) Is there evidence to support the claim that cotton content affects the mean tensile strength? Use = $ 0.05.

(b) Use the Fisher LSD method to make comparisons between the pairs of means. What conclusions can you draw?

(c) Analyze the residuals from this experiment and comment on model adequacy.

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Cotton Weight Percent Observations 15 20 12 25 14 30 19 35 72497 7 15 11 9 17 12 18 18 19 19 18 18 25 22 19 23 10 11 15 11