Bakers Ltd are currently undertaking a review of the delivery vans used to deliver products to customers. The company runs two types of delivery van (type A, recently purchased, and type B, at least three years old) which are supposed to be capable of achieving 20 km per litre of petrol. A new sample has now been collected, as given in Table 6.12.

(a) Assuming that the population distance travelled varies as a normal distribution, is there any evidence to suggest that the two types of delivery vans diff er in the mean distances travelled?

(b) Based upon your analysis, is there any evidence that the new delivery vans meet the mean average of 20 km per litre?

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A 17.68 18.72 26.49 26.64 9.31 22.38 20.23 28.80 17.57 9.13 20.98 Table 6.12 B 15.8 36.1 6.3 12.3 15.5 40.1 20.4 3.7 13.6 35.1 33.3 A 26.42 25.22 13.52 14.01 B 34.8 16.8 15.0 28.9 33.9 27.1 16.8 23.6 29.7 28.2