1. A biology professor is reviewing the final grades in her spring term cohort. She finds the mean grade to be x=87, with a margin of error of 3. Construct a confidence interval for the mean final grade. 2. The amounts of insurance claims that a car dealership submits each year are normally distributed with a population standard deviation of 4.5 claims and an unknown population mean. A random sample of 40 dealerships is taken and results in a sample mean of 32 claims. Find the margin of error for a 90% confidence interval for the population mean. z0.10 z0.05 z0.025 z0.01 z0.005 1.282 1.645 1.960 2.326 2.576 You may use a calculator or the common z values above. 3. In a recent survey, a random sample of 199 office managers were asked about overtime, and 76 reported that they regularly work overtime each week. What value of z should be used to calculate a confidence interval with a 98% confidence level? z0.10 z0.05 z0.025 z0.01 z0.005 1.282 1.645 1.960 2.326 2.576 4. Julia wants to estimate the percentage of high-school students who live in two-parent households. She surveys 160 high-school students and finds that 88 live in two-parent households. Identify the values needed to calculate a confidence interval at the 99% confidence level. Then find the confidence interval. z0.10 z0.05 z0.025 z0.01 z0.005 1.282 1.645 1.960 2.326 2.576 5. In a recent survey of 345 online business owners, 305 stated that they are interested in using discounted delivery services. Assuming the distribution is approximately normal, determine the point estimate and standard error for the proportion of online business owners who are interested in using discounted delivery services. 6. Chandra wants to estimate the percentage of people who smoke. She surveys 100 individuals and finds that 15 of them smoke. Find the margin of error for the confidence interval for the population proportion with a 98% confidence level. z0.10 z0.05 z0.025 z0.01 z0.005 1.282 1.645 1.960 2.326 2.576 7. The wait times at restaurants in Scottsdale during peak hours are normally distributed with a population standard deviation of 2 minutes and an unknown population mean. A random sample of 50 observations is taken and results in a sample mean of 18 minutes. Identify the parameters needed to calculate a confidence interval at the 90% confidence level. Then find the confidence interval. z0.10 z0.05 z0.025 z0.01 z0.005 1.282 1.645 1.960 2.326 2.576 8. The population standard deviation for the heights of dogs, in inches, in a city is 7.8 inches. If we want to be 95% confident that the sample mean is within 2 inches of the true population mean, what is the minimum sample size that can be taken? z0.10 z0.05 z0.04 z0.025 z0.01 z0.005 1.282 1.645 1.751 1.960 2.326 2.576