Given these facts:
Using the case of testing women for breast cancer (*)
1% have breast...
Given these facts:
Using the case of testing women for breast cancer (*)
1% have breast cancer
99% don’t have breast cancer
Mammogram tests
In event of a woman with cancer
80% of mammograms detect breast cancer when it is there
(positive)
20% miss it (false negative)
In event of no cancer
9.6% of mammograms detect breast cancer when it’s not there
(false positive)
90.4% correctly return a negative result.
Questions:
A lady takes the test three times and all three tests are
positive. What are the chance of her having
cancer?
A lady takes the test, and it shows negative, but
she is not convinced and so takes a second test. The second test is
positive. What are the chances that she has cancer?
A lady takes the test, and it shows negative, but
she is not convinced and so takes a second test, which still shows
negative. What are the chances that she has cancer?
A lady takes the test, and it shows positive, but
she is not convinced and so takes a second test. The second test is
negative. What are the chances that she has cancer?
Solutions
Expert Solution
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A mammogram was used to screen for breast cancer in 200 women
with breast cancer diagnosed by a biopsy and in 500 age- and
race-matched women without breast cancer. The results of the
mammogram were positive in 150 of the women with breast cancer and
in 100 of the women without breast cancer. b. Compute the i)
sensitivity, ii) specificity, iii) positive predictive value, and
iv) negative predictive value. c. Make a statement about each of
the computations d. If...
Exercise 1: Thirty nine women with a diagnosis of inoperable or
metastatic breast cancer have been followed-up for a number of
years, while under continuous treatment with a medication called
trastzuzumab. The time (in months) each patient remained in
remission was recorded. Remission is is a decrease or disappearance
of signs and symptoms of cancer. Below is the data. 50 74 35 39 21
37 27 35 30 35 26 38 34 34 26 41 61 33 33 26 25...
thirty-nine women with a diagnosis of inoperable or metastatic
breast cancer have been followed-up for a number of years, while
under continuous treatment with a medication called trastuzumab.
the time (in months) each patient remained in remission was
recorded. Remission is a decrease or disappearance of signs and
symptoms of cancer. Below is the data.
50 74 35 39 21 37 27 35 30 35 26 38 34 34 26 41 61 33 33 26 25
41 35 34 44...
Research Methond
Suppose that among 100,000 women with negative mammograms, 20
will have Breast Cancer (BC) diagnosed within 2 years; and among
100 women with positive mammograms, 10 will have BC diagnosed
within 2 years.
a. What is the Relative Risk (RR)?
b. What is the Risk Difference (RD)?
c. Restate your conclusion(s) in the form of a sentence.
One and a half percent (1.5%) of women over 55 have breast
cancer. Ninety-two percent (92%) of all women who have breast
cancer test positive on mammograms. Nine percent (9%) of women will
have false positive mammograms. Define the events: C: {a woman has
breast cancer} and +: {the mammogram is positive}.
a) Write down what is given in the problem, both explicitly and
implicitly, using the events defined in the problem
description.
b) If a randomly selected woman’s mammogram...
One and a half percent (1.5%) of women over 55 have breast
cancer. Ninety-two percent (92%) of all women who have breast
cancer test positive on mammograms. Nine percent (9%) of women will
have false positive mammograms. Define the events: C: {a woman has
breast cancer} and +: {the mammogram is positive}.
a) Write down what is given in the problem, both explicitly and
implicitly, using the events defined in the problem
description.
b) If a randomly selected woman’s mammogram...
16. An epidemiologic study of
breast cancer among elderly women followed 1,000 women, 65-79 years
of age, without evidence of breast cancer over several years. Every
two years the investigators examined the women for breast cancer.
The results were as follows: 12 new cases at the first evaluation,
11 new cases at the second evaluation, 23 new cases at the third
evaluation, and 28 new cases at the fourth (and final) evaluation.
The investigators also noted that 40 women had...
Patients with breast cancer sometimes die for other reasons. In
a Nurses’ Health study, women with breast cancer were followed
for 10 years and 2.5% had incidence of heart disease. Suppose the
baseline 10-year incidence rate of heart disease in the general
population is 2%. Assume a study is to be undertaken tracking
women with breast cancer to see if there is a difference in the
heart disease rate from the general population.
Assuming the true heart disease incidence rate...
A method currently used by doctors to screen women for possible
breast cancer fails to detect cancer in 20% of the women who
actually have the disease. A new method has been developed that
researchers hope will be able to detect cancer more accurately. A
random sample of 81 women known to have breast cancer were screened
using the new method. Of these, the new method failed to detect
cancer in 14. Let p be the true proportion of women...