a***o
发帖数: 118 | 1 1. suppose that 5% of people of your age and heredity have diabetes.
Suppose that a blood test has been developed that correctly gives a positive
test result in 80% of people with diabetes, and gives a false positive in
20% of the cases of people without diabetes. Suppose you take the test, and
it is positive. What is the probability that you actually have diabetes,
given the positive result?
我怎么觉得和5%无关呢? | x****r
发帖数: 99 | 2 有关系的， 假设
A: 得了糖尿病
B: 测试阳性
P(A) = 0.05;
P(B|A) = 0.8;
P(B|^A) = 0.2;
P(AB) = P(B|A) * P(A) = 0.8 * 0.05 = 0.04;
P(^AB) = P(B|^A) * P(^A) = 0.2 * 0.95 = 0.19;
P(B) = P(AB) + P(^AB) = 0.23;
现在求P(A|B) = P(AB) / P(B) = 0.04 / 0.23 = 4/23
P(A|B)就是测试阳性下你得糖尿病的概率
上课这样教的，不对请指正 ：Ｐ
positive
positive in
test, and
diabetes,
【在 a***o 的大作中提到】
: 1. suppose that 5% of people of your age and heredity have diabetes.
: Suppose that a blood test has been developed that correctly gives a positive
: test result in 80% of people with diabetes, and gives a false positive in
: 20% of the cases of people without diabetes. Suppose you take the test, and
: it is positive. What is the probability that you actually have diabetes,
: given the positive result?
: 我怎么觉得和5%无关呢?
| a***o
发帖数: 118 | |
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