Suppose routine blood typing for 400 army recruits reveals that 6 of them have AB negative blood.
a. What assumptions would you have to make for this to be considered a random sample of army personnel? Of the entire country?
b. Place an approximate 80% confidence interval on the proportion with AB-negative blood among army recruits.
c. Assuming it can be justified, place an approximate 80% confidence interval on the proportion of those with AB-negative blood in the entire country.