Diagnostic test measures

1. 5 POINTS: A recent publication (see paper which will be released once you submit this assignment) provides details about a new diagnostic test for COVID-19 compared to the gold standard PCR testing. A total of 386 people were tested using the new procedure and PCR testing. 71 people tested positive by PCR, while 67 tested positive by the new test. 315 tested negative by PCR and the new test.

Complete the 2 x 2 table below:

Calculate:

Prevalence

Sensitivity

Specificity

False Positive Rate

False Negative Rate

Positive Predictive Value (PPV)

Negative Predictive Value (NPV)

Interpret what each of these measures means.

2. 5 POINTS: Calculate what would happen to the false positive and false negative rates, and PPV and NPV, if you kept sensitivity and specificity constant (as calculated in Question 1), but used this test in 1,000 people in an area with an expected prevalence of 10%. Interpret all of your results.

Complete the 2 x 2 table below:

Calculate:

False Positive Rate

False Negative Rate

Positive Predictive Value (PPV)

Negative Predictive Value (NPV)

Interpret what each of these measures means and the meaning of each of the changes.

3. 5 POINTS: Calculate what would happen to the false positive and false negative rates, and PPV and NPV, if the sensitivity changed to 85% and specificity changed to 90%, in 1,000 people in an area with an expected prevalence the same as calculated in Question 1. Compare these to the results Interpret all of your results.

Complete the 2 x 2 table below:

Calculate:

False Positive Rate

False Negative Rate

Positive Predictive Value (PPV)

Negative Predictive Value (NPV)

Interpret what each of these measures means and the meaning of each of the changes.

Grading: Grades are based on whether you attempted each question, NOT based on correct answers right now. You must make a legitimate attempt to earn the points.