You can use "p-hat" for sample proportion, p for population proportion, "x-bar" for sample mean, zc (z-critical) instead of Zalpha/2, tc (t-critical) instead of talpha/2, "mu" for population mean, "sigma" for population standard deviation, and s for sample standard deviation. 1. A recent study of 750 internet users in Europe found that 35% of internet users were women. What is the 95% confidence interval of the true proportion of women in Europe who use the internet? 2. It was found that in a sample of 90 teenage boys, 70% of them have received speeding tickets. What is the 90% confidence interval of the true proportion of teenage boys who have received speeding tickets? 3. A quality control expert wants to estimate the proportion of defective components that are being manufactured by his company. A sample of 300 components showed that 20 were defective. How large a sample is needed to estimate the true proportion of defective components to within 2.5 percentage points with 99% confidence? 4. A food snack manufacturer samples 11 bags of pretzels off the assembly line and weighs their contents. If the sample mean is 14.7 oz. and the sample standard deviation is 0.70 oz., find the 95% confidence interval of the true mean. 5. A previous analysis of paper boxes showed that the standard deviation of their lengths is 9 millimeters. A packer wishes to find the 98% confidence interval for the average length of a box. How many boxes does he need to measure to be accurate within 3 millimeters? NOTE: 98% not in table, conversion is 98% confidence->Zc=2.33 6. A study of 75 apple trees showed that the average number of apples per tree was 725. The standard deviation of the population is 100. What is the 99% confidence interval for the mean number of apples per tree for all trees