Confidence Intervals for proportions

The Department of Transportation reported Amtrak trains had a 78% on-time arrival record over the previous 12 months (USA Today, November 23, 1998). Assume that in 2001, a study found 330 of 400 Amtrak trains arrived on time. Does the sample indicate the Amtrak arrival rate has changed? Test at a 95% confidence interval.

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