The IQs of a class of students attending a university are distributed according to the normal curve, with a mean of 115 and a standard deviation of 10. Therefore:
a. 50% have IQs between 105 and 115.
b. 95% have IQs between 105 than 115.
c. 2.5% have IQs above 135.
d. 5% will have IQs above 135.
e. 5% have IQs below 95.
The IQs of a class of students attending a university are distributed according to the normal curve, with a mean of 115 and a standard deviation of 10. Therefore:
a. 50% have IQs between 105 and 115.
b. 95% have IQs between 105 than 115.
c. 2.5% have IQs above 135.
d. 5% will have IQs above 135.
e. 5% have IQs below 95.
The IQs of a class of students attending a university are distributed according to the normal curve, with a mean of 115 and a standard deviation of 10. Therefore:
a. 50% have IQs between 105 and 115.
b. 95% have IQs between 105 than 115.
c. 2.5% have IQs above 135.
d. 5% will have IQs above 135.
e. 5% have IQs below 95.
mean 115 +/-10(which is 68%= 1SD) means the range is between 105-125
range at 95% will be 2SD 2*10 = 115 +/-20, will be between 95-135 (NOT between 105-115)
range at 99% ( after 2SD:95%, remaining total percent is 5% = 3SD or 2.5% EACH side): means 2.5% will have IQ below 95 and 2.5% will have IQ above 135. because between 95-135 is 2SD (95%). so if you go below 95 or if you go above 135, you will go into 3SD (99%) range.
therefore, only option C matches the results.
A new serologic test for detecting prostate cancer is negative in 95% of the patients who do not have the disease. If the test is used in eight 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. 0.05^8
D. 0.95^8
E. 1-0.95^8
A new serologic test for detecting prostate cancer is negative in 95% of the patients who do not have the disease. If the test is used in eight 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. 0.05^8
D. 0.95^8
E. 1-0.95^8
1. Negative in 95% = Specificity
2. Used 8 samples
3. What's probability of getting all negative? All negative = 0.95^8
4. What's probability of getting at least 1 positive? That would be
1 - Probability all negative = 1 - 0.95^8.
5. My answer is E.
As the probability of getting negative test result is 95%, the probability of getting a positive test is 5%. As we should get atleast 1 positive result out of 8 samples which is a mutually exclusive event, 0.05 * 8 would be the correct answer.
If the question says all the 8 results should come positive then the answer would be 0.05 ^ 8. I am not so sure. If somebody know the answer correctly please explain........
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Related Threads
?
?
?
?
?
USMLE Forums
402.5K posts
115.1K members
Since 2009
A forum community dedicated to the United States Medical Licensing Examination. Come join the discussion about schools, exams, news, prep, reviews, accessories, classifieds, and more!