1. When a 'gooing' machine is working properly, filled chocolate bars have an average weight of...

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1. When a 'gooing' machine is working properly, filled chocolate bars have an average weight of 30g with a standard deviation of 1g. For quality control a sample of 50 bars is taken during the course of a day and the average weight, x, is calculated. At the end of a particular day the sample average is 29.7. Calculate a 95% confidence interval for the mean weight of a bar on this day. 2. Calculate a 98% confidence interval for the mean weight of the bars described in question 1. Would you expect this interval to be wider or narrower than the interval calculated in question 1? 3. A regular daily flight is due to arrive at 1800 hours. Its arrival time has a normal distribution with mean 1810 hours and standard deviation 10 minutes. A new air-traffic control system is installed but is criticised for causing delays in arrivals. To investigate this a sample of 20 flights gave a mean arrival time of 1812 hours. Give 95% confidence limits for the new mean arrival time. 1. When a 'gooing' machine is working properly, filled chocolate bars have an average weight of 30g with a standard deviation of 1g. For quality control a sample of 50 bars is taken during the course of a day and the average weight, x, is calculated. At the end of a particular day the sample average is 29.7. Calculate a 95% confidence interval for the mean weight of a bar on this day. 2. Calculate a 98% confidence interval for the mean weight of the bars described in question 1. Would you expect this interval to be wider or narrower than the interval calculated in question 1? 3. A regular daily flight is due to arrive at 1800 hours. Its arrival time has a normal distribution with mean 1810 hours and standard deviation 10 minutes. A new air-traffic control system is installed but is criticised for causing delays in arrivals. To investigate this a sample of 20 flights gave a mean arrival time of 1812 hours. Give 95% confidence limits for the new mean arrival time.

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