General Direction: Copy and answer each problems. 1. The approximate costs for a 30-second spot for various cable networks in a random selection of cities are shown below. Estimate the true population mean cost for a 30-second advertisement on cable network with 90% confidence. Was the interval estimate accurate if the true population mean cost for a 30-second advertisment on cable network is 40? 14 55 165 9 15 66 23 30 22 12 13 54 73 55 41 78 Source www.spotrunner.com 150 2. A confidence interval estimate is desired for the gain in a circuit on a semiconductor device. Assume that the gain is normally distributed with = 400, n = 25, and X = 9,700. Was the 90% Cl accurate if the true mean of the gain is 10,000? 3. Assume that women's heights are normally distributed with a mean given by = 62.3 inches and a standard deviation = 1.8 inches. If a woman is randomly selected, find the probability that her height is between 61.7 inches and 62.7 inches? 4. A university dean wishes to estimate the average number of hours that freshmen study each week. The standard deviation from a previous study is 2.6 hours. How large a sample must be selected if he wants to be 99% confident of finding whether the true mean differs from the sample mean by 0.5 hour? 5. In a study of 10 insurance sales representatives from a certain large city, the average age of the group was 48.6 years and the standard deviation was 4.1 years. Assume the variable is normally distributed. Find the 95% confidence interval of the population mean age of all insurance sales representatives in that city. 6. In a hospital, a sample of 8 weeks was selected, and it was found that an average of 438 patients was treated in the emergency room each week. The standard deviation was 16. Find the 99% confidence interval of the true mean. Assume the variable is normally distributed.