# arm – Practice Test 3

### Practice Test 3

arm – 这个题目属于一个arm的代写任务, 是有一定代表意义的arm等代写方向

``````Practice Test 3
``````
1. How many permutations of lengthnare there that arenot(n2)-stack sortable?
2. (This is Supplementary Exercise 15.34.) A medical device for testing whether a patient has a certain type of illness will accurately indicate the presence of the illness for 99 percent of patients who do have the illness, and will set off a false al arm for five percent of patients who do not have the illness. Let us assume that only three percent of the general population has the illness.
``````(a) If the test indicates that a given patient has the illness, what is
the probability that the test is correct?
(b) If the test indicates that a given patient does not have the illness,
what is the probability that the test is correct?
(c) What percentage of the test results provided by this device will
be accurate?
``````
1. Albert and Brenda each tossed a fair coin ten times. What is the probability that each of them got five tails if we know that the two people got the same number of tails?