Question

A local company installs natural-gas grills. As part of the installation, a ditch is dug to lay a small natural-gas line from the grill to the main line. On the average, the depth of these lines seems to run about 1 foot. The company claims that the depth does not vary by more than 16 square inches (the variance). To test this claim, a researcher randomly took 22 depth measurements at different locations. The sample average depth was 13.4 inches with a standard deviation of 6 inches. Is this enough evidence to reject the company’s claim about the variance? Assume line depths are normally distributed. Let α = .05.



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  • CreatedFebruary 19, 2015
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