(a)If you have no preliminary estimate for p, how many medical files should you include in a random sample in order to be 81% sure that the point estimate p will be within a distance of 0.04 from p?

Find the critical value for 81% confidence level, z_0.81,

and find the specified maximal error of estimate, E. (Round your answers to two decimal places.)

z_0.81=

E=

Compute the minimal sample size n for estimating the proportion p of all people who have blood type B under these restrictions. (Round your answer to a whole number.)

n = medical files

(b)Answer part (a) only this time use the preliminary estimate that about 13 out of 85 people have blood type B. (Round your proportions to three decimal places and your minimum sample size to a whole number.)

p=

q=

n= medical files