Ch8-9 quiz Name: 1. You wish to estimate, with 95% confidence, the percentage of all U.S. adults who think that the high price of gasoline is the fault of the current president. Your estimate must be accurate within 2.5% of the population proportion. (a) (5 points) No preliminary estimate is available. Find the mini- mum sample size needed. (b) (5 points) Find the minimum sample size needed, using a prior study that found that 48% of U.S. adults think that the high price of gasoline is the fault of the current president. 2. (5 points) Students An admissions director wants to estimate the mean age of all students enrolled at a college. The estimate must be within 1 year of the population mean. Assume the population of ages is nor- mally distributed. Determine the minimum sample size required to construct a 90% confidence interval for the population mean. Assume the population standard deviation is 1.2 years. 3. (5 points) A meteorologist who sampled 13 thunderstorms found that the average speed at which they traveled across a certain state was 15 miles per hour. The standard deviation of the sample was 1.7 miles per hour. Find the 99% confidence interval of the mean. If a meteorolo gist wanted to use the highest speed to predict the times it would take storms to travel across the state in order to issue warnings, what figure would she likely use? Assume the variable is normally distributed. 4. (5 points) Thirty-five percent of adult Americans are regular voters. A random sample of 250 adults in a medium-size college town were surveyed, and it was found that 110 were regular voters. Estimate the actual proportion of regular voters with 90% confidence and comment on your results