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  #1  
Old 03-09-2012
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Stats probability question!

A serological test for detecting prostate cancer is negative in 95% of the cases. If the test is used with 8 consecutive blood samples taken from patients without the disease, what is the probability of getting at least one positive test result?
A. 1-0.05*8
B. 0.05*8
C. 0.05 raised to the power 8
D. 0.95 raised to the power 8
E. 1-0.95 raised to the power 8

Please answer with explanation.
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  #2  
Old 03-09-2012
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A serological test for detecting prostate cancer is negative in 95% of the cases. If the test is used with 8 consecutive blood samples taken from patients without the disease, what is the probability of getting at least one positive test result?
A. 1-0.05*8
B. 0.05*8
C. 0.05 raised to the power 8
D. 0.95 raised to the power 8
E. 1-0.95 raised to the power 8

Explanation
Test is Truly Negative in 95% of the cases, and Falsely Positive in 5%. The scenario states that the test is used with 8 blood samples. Each testing should be assumed to be an independent event. Than mean that each time the test is performed in 1 blood sample there is 0.95 (95%) probabilities that the test will give a True Negative result and 0.05 (5%) probabilities that the test will give a False Positive result.
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  #3  
Old 03-09-2012
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Default why not c?

why is it not c?? ughhhhh i was never good with the exponents stuff
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Old 03-09-2012
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Arrow .05*8

Quote:
Originally Posted by bunny View Post
A serological test for detecting prostate cancer is negative in 95% of the cases. If the test is used with 8 consecutive blood samples taken from patients without the disease, what is the probability of getting at least one positive test result?
A. 1-0.05*8
B. 0.05*8
C. 0.05 raised to the power 8
D. 0.95 raised to the power 8
E. 1-0.95 raised to the power 8

Explanation
Test is Truly Negative in 95% of the cases, and Falsely Positive in 5%. The scenario states that the test is used with 8 blood samples. Each testing should be assumed to be an independent event. Than mean that each time the test is performed in 1 blood sample there is 0.95 (95%) probabilities that the test will give a True Negative result and 0.05 (5%) probabilities that the test will give a False Positive result.
isn't the question asking false positive ?
which is .05 per patient and to get value for all
.05*8??????
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  #5  
Old 03-25-2012
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Default anyone??

can any1 explain this please?? I think the answer is C. i dont understand why it is E ... UW says its E .. i just dont get it!
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  #6  
Old 03-25-2012
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Default

all i know is this --> C & E are the same!!

C. 0.05 raised to the power 8
E. 1-0.95 raised to the power 8

explanation? because 1 -0.95 = .05

i sure do know my math :P
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  #7  
Old 03-25-2012
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Quote:
Originally Posted by drhma View Post
all i know is this --> C & E are the same!!

C. 0.05 raised to the power 8
E. 1-0.95 raised to the power 8

explanation? because 1 -0.95 = .05

i sure do know my math :P
lol no let me re-write that one. option E. is 1-(0.95raised to the power 8!) .. C & E are different! my bad, i didnt write the options clearly!
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