(mg/dl) obtained from the survey (HDL is "good" cholesterol; the higher its value, the lower the risk for heart disease). (a) Calculate a point estimate (in mg/dl ) of the population mean HDL cholesterol level. mg/dl from the smallest 50%. mg/dl (c) Calculate a point estimate (in mg/dl ) of the population standard deviation. (Round your answer to three decimal places.) mg/dl (d) An HDL level of at least 60 is considered desirable as it corresponds to a significantly lower risk of heart disease. Making no assumptions about the shape of the population distribution, estimate the proportion p of the population having an HDL level of at least 60. p=