People were polled on how many books they read the previous year. How many subjects are needed to estimate the number of books read the previous year within one book with 90 % confidence? Initial survey results indicate that sigma Equals 10.4 books. A 90 % confidence level requires nothing subjects A doctor wants to estimate the HDL cholesterol of all 20- to 29year-old females. How many subjects are needed to estimate the HDL cholesterol within 4 points with 99 % confidence assuming sigma equals 15.9 question mark Suppose the doctor would be content with 95 % confidence. How does the decrease in confidence affect the sample size required? A 99% confidence level requires nothing subjects