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a)suppose that a Saudi steel pipe co.. a versatile producer of a special-purpose type of pipe,...

a)suppose that a Saudi steel pipe co.. a versatile producer of a special-purpose type of pipe, is interred in testing the hypothesis that that the mean diameter of the pipes is 25.5cm. A sample of 81 pipes is randomly selected and yields a mean of 25.46cm and standard deviation of 0.2cm. is there evidence that the mean diameter of the pipes is different from 25.5cm? use a 0.01 significance level

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