A company that makes computers must transport them from its warehouse to the delivery centre, with one lorry delivery per day. In three weeks' time, the usual route will have roadworks stopping the traffic for six weeks. The local council says that the alternative route will add not more than ten minutes to the route. The manager of the company does not think that this is true and so, for the next 14 days, he asks eight of the company's lorry drivers to travel the new route, and six to travel the old route.

a. Find S²_p, the pooled estimate of the population variance.

b. Test, at the 5% significance level, whether the manager is justified in his complaint assuming the times are normally distributed.

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