1:Blood banks will shortly start to screen all donors for NANB hepatitis. Although the new screening tests are estimated to disqualify up to 5 percent of all prospective blood donors, they will still miss two-thirds of donors carrying NANB hepatitis. Therefore, about 10 percent of actual donors will still supply NANB contaminated blood.
the argument above depends on which of the following assumptions?
a: Donors carrying NANB hepatitis do not, in a large percentage of cases, carry other infections for which reliable screenting tests are rountinely performed。
b; donors carrying NANB hepatitis do not, in a large percentage of cases ,develop the disease themselves at any point.
c;the estimate of the number of donors who would be disqualified by tests for NANB hepatitis is an understimate.
d; The incidence of NANB hepatitis is lower among the potential blood donors than it is in the population at large.
e;the donors who will still supply NANB contaminated blood will donate blood at the average frequency for all donors.
用有关无关排出应该能得出A,但是A如何更好的解释呢?
2:Theprice the government for standard weapons puchased from military contractors is determined by a pricing method called"historical costing"historical costing allows contractors to protect their profits by adding a percentage increase,based on the current rate of inflation,to the previous year's contractual price.
which of the following statements,if true,is the best basis for a criticism of historical costing as an economically sound pricing method for military contracts?
a;the government might continue topay for past inefficient use of funds.
b;the rate of inflation has varied considerable over the past twenty years.
(why a not b?)
thx. |