[問題]大全2-19

[vitality]

Q 19-20 are based on the following.

Blood banks will shortly start to screen all donors for NANB hepatitis. Although the new screening tests are estimated to disqualify up t o5 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 suppy NANB-contaminated blood.

19. The arguement above depends on which of the following assumption?

(A) Donors carrying NANB hepatities do not, in a large percentage of
cases, carry other infections for which reliable screening tests are
routinely performed.

(B) Donors carrying NANB hepatities 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 underestimate

(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.

----->答案為何是(A)呢?

[Behemoth]

請一帖一題喔

感謝您~

[Calvin]

Hi, vitality

又是我~~

請問妳認為的正確答案是？又為何妳不選A呢？

把妳的思路說出來，會讓討論更有效率及幫助喔！

[DARY]

Q 19-20 are based on the following.

Blood banks will shortly start to screen all donors for NANB hepatitis. Although the new screening tests are estimated to disqualify up t o5 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 suppy NANB-contaminated blood.

19. The arguement above depends on which of the following assumption?

(A) Donors carrying NANB hepatities do not, in a large percentage of
cases, carry other infections for which reliable screening tests are
routinely performed.

(B) Donors carrying NANB hepatities 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 underestimate

(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.

----->答案為何是(A)呢?

they will still miss two-thirds of donors carrying NANB hepatitis
(A)表示這2/3的捐血者是真的可以捐血的，亦support這些人是被誤判的

[vitality]

Hi Dary and Calvin,

謝謝你們 我好像有點懂了 只是還不大確定 想要請教兩位一下

題目的意思好像是說即使有檢查出5percent的捐血者是不合格的 但仍然有2/3帶有NANB hepatitis沒有被查出來 因此還有大約10 percent的人仍帶有NANB-contaminated blood.

X =所有blood donors中感染NANB hepatitis的比率
5%* all people=all people*X*1/3
X=15%
15%* 2/3=10% 所有blood donors中感染NANB hepatitis的還有10%沒有
被查出來

而題目說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…..

題目假設的計算方式 是只要disqualify的就是帶有NANB的 而答案(A) 說明了只要帶有NANB就不會帶有其他的感染物 可以支持檢查題目假設的計算方式 disqualify=有NANB的 若少了這個假設就有可能有其他的感染物可以使blood donors disqualify….

我當初選不大出來 有一部分原因就是不知道他說的那5% disqualified是指針對NANB hepatitis 篩檢 還是針對所有疾病~~~

不知道我想的對不對 還要請大家幫忙解答囉~~

[Calvin]

原題題意妳的解釋沒錯

但選項A，我的解讀與妳不同
選項A說的是帶有NANB的捐血者不會帶有其他例行性做的screening test可以有效檢測出來的感染病（好難翻，暈…）
這個意思就是說，如果NANB的捐血者，若同時帶有其他可被檢測出來的感染病毒的話，那即使逃過NANB檢查的人，也會因為被查出有其他的infections而被kick out，那結論Therefore, about 10 percent of actual donors will still suppy NANB-contaminated blood. 就不能成立了。
能夠supply NANB-contaminated blood一定小於10%，因為被other reliable screening tests 給 eliminate了！

希望有解答到妳的疑問，不了解歡迎繼續提問！

FYI

[vitality]

Hi Calvin,

謝謝你啦 你還幫我完整翻譯出(A)選項 我也覺得那句好難翻~~
終於搞懂這一題了~~~

[micht]

感謝Calvin i57

[A級垂耳兔]

可以請問一下(E)為何錯誤?
我的想法是:帶原者持續捐血才能維持15%的帶原率...我的想法哪裡錯了?
而且我覺得A選項與題目主軸THEREFORE,後面無關

[dibert8]

這題的推論有兩種可能:1.篩選只做 NANB hepatities, 2. (A)

(B) 無關
(C) 沒有根據
(D) 題目沒有區分 donors 跟 population at large
(E) 題目的百分比都是針對 donors, 不需再另外假設捐血頻率 (i.e. 捐多少次結論都是一樣的,平均不平均也不會有影響).