What does it mean to say that the confidence interval methods for the mean are robust against departures from normality? choose the correct answer below. a. the confidence interval methods for the mean are robust against departures from normality, meaning they only work with distributions that aren't normal. b. the confidence interval methods for the mean are robust against departures from normality, meaning they work well with distributions that aren't normal, provided that departures from normality are extreme. c. the confidence interval methods for the mean are robust against departures from normality, meaning they work well with distributions that aren't normal, provided that departures from normality are not too extreme. d. the confidence interval methods for the mean are robust against departures from normality, meaning they don't work well with distributions that aren't normal?

5. understanding marginal and average tax rates consider the economy of citronia, where citizens consume only oranges. assume that oranges are priced at $1 each. the government has devised the following tax plans: plan a • consumption up to 1,000 oranges is taxed at 50%. • consumption higher than 1,000 oranges is taxed at 20%. plan b • consumption up to 2,000 oranges is taxed at 15%. • consumption higher than 2,000 oranges is taxed at 60%. use the plan a and plan b tax schemes to complete the following table by deriving the marginal and average tax rates under each tax plan at the consumption levels of 300 oranges, 1,200 oranges, and 3,000 oranges, respectively. consumption level plan a plan b (quantity of oranges) marginal tax rate average tax rate marginal tax rate average tax rate (percent) (percent) (percent) (percent) 300 1,200 3,000 complete the following table by indicating whether each plan is a progressive tax system, a proportional tax system, or a regressive tax system. progressive proportional regressive plan a plan b