Please answer the following. Take a picture of your solution and box your answer. Then upload it for submission. 1. The decibel levels of noise at numerous urban hospitals in the vicinity were measured. The mean noise level in 84 corridors was 61.2 dB, with a population standard deviation of 7.9. Determine the true mean's 95% confidence interval. 2. A researcher wishes to estimate within P20 the average cost of postage a community college spends in one year. If she wishes to be 90% confident, how large of a sample would be necessary if the population standard deviation is P60. 3. The lengths (in minutes) of a random selection of popular children's animated films are listed below. Estimate the true mean length of all children's animated films with 95% confidence. 93, 83, 76, 92, 77, 81, 78, 100, 78, 76, 75 4. According to a recent poll of eight social networking sites, the average monthly visitor count was 12.1 million. The standard deviation was 3.1 million. Find the real mean's 94 percent confidence interval