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Variation and Quality: A sign of quality is low variation in the dimensions of key manufactured components for a product. For example, a study looked at 25 shelves that were designed for a bookcase sold at the retail chain Wal-mart. This bookcase needed to be put together by the customer. They found that the variance for the shelf lengths was 9.23 mm² (the shelves were supposed to be 670 mm long in order to fit into the case properly). Another 27 shelves produced by Basset furniture were examined, and it was found that the variance for those shelf lengths was 0.25 mm². At the 5% significance level, test the claim that the shelves sold at Wal-Mart are manufactured with more variation than the shelves produced by Basset.