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 don't work well 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 not too 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 extreme. d. the confidence interval methods for the mean are robust against departures from normality, meaning they only work with distributions that aren't normal.