Statistics

You want to obtain a sample to estimate a population mean. Based on previous evidence, you believe the population standard deviation is approximately o = 79.1. You would like to be 90% confident that your esimate is within 2.5 of the true population mean. How large of a sample size is required? n = 2 In a survey, 26 people were asked how much they spent on their child's last birthday gift. The results were roughly bell-shaped with a mean of $40 and standard deviation of $8. Construct a confidence interval at a 90% confidence level. Give your answers to one decimal place. 3 In a survey, 20 people were asked how much they spent on their child's last birthday gift. The results were roughly bell-shaped with a mean of $31 and standard deviation of $7. Construct a confidence interval at a 80% confidence level. Give your answers to one decimal place. Insurance companies are interested in knowing the population percent of drivers who always buckle up before riding in a car. They randomly survey 402 drivers and find that 306 claim to always buckle up. Construct a 86% confidence interval for the population proportion that claim to always buckle up. Use Brackets [ ], for interval. We wish to estimate what percent of adult residents in a certain county are parents. Out of 100 5 adult residents sampled, 23 had kids. Based on this, construct a 90% confidence interval for the proportion, p, of adult residents who are parents in this county. Give your answers as decimals, to three places