Question

In the following scenarios identify the Reality, the test, Sensitivity, Specificity, False Negative, and False Positive. Then explain which is worse (if either) a False Negative or a False Positive.

2. A test is done to determine the sex of snails. (Consider Male to be positive and Female negative)

a. Reality:

b. Test:

c. Sensitivity:

d. Specificity:

e. False Negative:

f. False Positive:

g. Which is worse:

Answer #1

a. Reality: Snail is Male.

b. Test: Test correctly identifies given snail as Male.

c. Sensitivity: Among all the snailes which are male, the proportion of snails identified as male by the test.

d. Specificity: Among all the snailes which are female, the proportion of snails identified as female by the test.

e. False Negative: Snail is actually Male and test identifies it as female.

f. False Positive: Snail is actually female and test identifies it as male.

g. Which is worse: Both False negative and false positive are equally worse in this case.

You are evaluating a the sensitivity
and specificity of a screening test.
Disease Positive
Disease Negative
Screen Positive
20
150
Screen Negative
5
9640
Calculate the sensitivity of the screening test.
Calculate the specificity of the screening test.

In medical diagnosis, test sensitivity is the ability of a
test to correctly identify those with the disease (true positive
rate), whereas test specificity is the ability of the test to
correctly identify those without the disease (true negative rate).
This means that:
• Sensitivity of test = P(test is positive | person has
disease);
• Specificity of test = P(test is negative | person does not
have disease).
Suppose that 1% of the population have a particular disease,
and...

Calculate the % sensitivity and % specificity of urine
pregnancy test given the data below. (Hint: You will first have to
determine if the number in the column is a true positive, true
negative, false positive, or false negative before calculating
sensitivity and specificity of the test)
Table of Number of Pregnancies and Urine Pregnancy test
Results
Patient is Pregnant?
Patient has positive pregnancy test
Patient has negative pregnancy test
Row totals
Yes
32
8
40
No
5
143
148...

Explain the problem with having false negative passengers?
Specificity measures the likelihood of a test being negative
given someone does not have the disease. Articulate what the
specificity would tell us in context to screening passengers in an
airport?
Sensitivity measures the likelihood of a test being positive
given someone has the disease. Articulate what the sensitivity
would tell us in context to screening passengers in an airport?

Using the following
2x2 table calculate the prevalence of the disease , sensitivity of
the test, specificity of the test , predictive value of a positive
test
Disease
Present
Absent
Test Result
Positive
34
20
Negative
116
9830
Prevalence
Sensitivity
Specificity
Predictivity value of
a positive test
A.
99.7%
B.
31%
C.
63%
D.
1.5%
E.
59%
F.
22.6%
G.
25%

A study was done to evaluate the sensitivity and specificity of
an electrocardiography (ECG) test for detecting left ventricular
hypertrophy (LVH), a binary measure of cardiovascular disease. The
authors reported the following results from their sample of 1562
men. Assume that these 1562 men were randomly sampled from the
population of males.
LVH = Yes
LVH = No
Test positive
20
198
Test negative
26
1318
(*) What are the sensitivity and specificity of the ECG test
for detecting LVH...

Suppose that a screening test for breast cancer has 95%
sensitivity and 90% specificity. Assume 1% of the population being
screened truly has breast cancer.
a. If you really do have breast cancer, what is the probability
that the test says you do?
b. If you really do not have breast cancer, what is the
probability that the test says you do?
c. The screening test is applied to a total of 15 people; 5 who
really do have cancer...

7) For the following example, identify the following.
3O2 (g) → 2O3(g)
A) a negative ΔH and a negative ΔS
B) a positive ΔH and a negative ΔS
C) a negative ΔH and a positive ΔS
D) a positive ΔH and a positive ΔS
E) It is not possible to determine without more information.

26) Which of the following statements is true when describing
Sensitivity?
Question 26 options:
A)
It relates to how a practitioner interprets a test result.
B)
It is the ability of a test to correctly identify people who
have the disease you are testing for.
C)
It tells you the probability that a test reflects a person who
has the disease.
D)
It measures the effectiveness of a test in returning a negative
test result to people who do not...

Community health workers were conducting a screening test for
diabetes. People who tested positive on the screening test were
referred for follow-up testing to confirm if they had diabetes.
There were 300 people who tested positive
during the screening in the community. Thirty of these people were
later found to not have diabetes. There
were 500 people who tested negative during the screening in the
community. The community health workers later found out that 20 of
the people who tested...

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