Many cities have adopted High Occupancy Vehicle (HOV) lanes to speed commuter traffic to downtown business districts. Planning for Metro Transportation District has depended on a well- established average of 3.4 passengers per HOV. But a summer intern notes that because many firms are sponsoring van pools, the average number of passengers per car is probably higher. The intern takes a sample of 23 vehicles going through the HOV lane of a toil plaza and reports a sample mean of 4.3 passengers, and a standard deviation of 1.5 passengers. At the 0.01 level of significance, does the sample suggest that the mean number of passengers has increased?

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