Question

Statistic Someone help need help ASAP

. The tests done to determine if someone is HIV positive are called Enzyme immunoassay or EIA tests. The test screens a blood sample for the presence of antibodies to HIV. Like most tests, this test is not perfect. The table below shows the approximate probabilities of positive and negative EIA tests when the blood does and does not actually contain the HIV antibodies. Long range studies have shown that only 2% of the population actually has the HIV antibodies.
Test Result Positive Negative
Antibodies Present 0.9985 0.0015
Antibodies Not Present 0.006 0.994


a) Explain in context all four values in the table. That is, what does each of them actually mean?

Construct a tree diagram to answer the following questions. The first two choices of the tree should be whether or not the antibodies are present. The second choice should be the test result. (What is the probability split for the first choice?)

b) What is the probability that a person without HIV will have a test come out positive (this is called a false-positive)?
c) What is the probability that a person with HIV will have a test come out negative (this is called a false negative)?
d) What is the probability that a person with HIV will have a test

Answer 1

which part you're stuck on ?

Answer 2

B,C,AND D AND DIAGRAM

Answer 3

oh you're done wid part A... nice :)
lets draw the tree diagram

Answer 4

content is a. 99.85%,, 0.6%, 0.15% and 99.4%

Answer 5

ok and you do the antiobodies the same way

Answer 6

^^
2% really have HIV antibodies present
that gives 98% dont ahve HIV antibodies present

okay ?

Answer 7

ok

Answer 8

thats the complete tree,
let me knw if smthng doesnt make sense

Answer 9

ok

Answer 10

I understand

Answer 11

good, lets look at part b

Answer 12

thanks

Answer 13

b) What is the probability that a person without HIV will have a test come out positive (this is called a false-positive)?

Answer 14

do I need to look at the diagram to figure out b

Answer 15

do I need to divide something by 6

Answer 16

nope, we're given that the person has no HIV,
so u need to look in "Not present" branchb

Answer 17

the probability for a person without HIV to be reported as positive = 0.006
or 0.16%

Answer 18

we're done with part b)
see if that makes some sense

Answer 19

how did you get 16%

Answer 20

ok but how you got .16% what did you divide?

Answer 21

to change the probability 0.006 to percent, just multiply it by 100

Answer 22

ok

Answer 23

sorry typoes, let me correct it :)

Answer 24

corrected below :

the probability for a person without HIV to be reported as positive = 0.006
or 0.6%

Answer 25

see if that looks okay :)

Answer 26

so .9985 will be C and multiply .9985 *100=99.85