STA 210 Final Exam - Ch. 8

7b. What is the specificity for the test based on these screening results (rounded to three decimal places)?

0.000

4b. What is the chance the condition will be present, given the test came back negative, for the Ottawa Ankle Test (rounded to two decimal places)?

0.09

4f. The prevalence of a condition is just the probability that the condition will be present in the population studied. What is the prevalence based on each of the two sets of screening data?

0.22 based on the first; 0.93 based on the second

6a. What is the sensitivity of the test based on these screening results (rounded to three decimal places)?

0.400

7c. What is the overall accuracy for this gender screening test based on the screening results above (answer rounded to three decimal places)?

0.809

4e. What is the chance the condition will be present, given the test comes back negative, for the Ottawa Ankle Test based on these new screening results (rounded to two decimal places)?

0.81

6c. What is the overall accuracy for this cancer screening test based on the screening results above (answer rounded to three decimal places)?

0.922

7a. What is the sensitivity of the test based on these screening results (rounded to three decimal places)?

0.948

6b. What is the specificity for the test based on these screening results (rounded to three decimal places)?

0.949

4a. What is the sensitivity of the test (rounded to two decimal places)?

0.95

4d. Now let's change the data and suppose the screen test produced the results shown in Table 8.17. What is the sensitivity of the test based on these new screening results (rounded to two decimal places)?

0.95

1g. How often did the error saying "negative" when the patient really did have bowel cancer occur?

1 time

1e. How often did the error of saying "positive" when the patient really didn't have bowel cancer occur?

18 times

2b. Suppose we change the rule to say that any score in any of the three categories that is a "3" or higher means the roadside test tagged the participant as drunk. This is what the table of counts will look like with this new rule. According to this new table, what is the specificity of the FST with this new rule?

18/29

2d. According to this new table, what is the negative predictive value of the FST with this new rule?

18/40

1b. How many times did the FOB make the right decision?

184

2c. According to this new table, what is the positive predictive value of the FST with this new rule?

245/256

2e. According to this new table, what is the sensitivity of the FST with this new rule?

245/267

3a. Change the rule as needed and find the remaining six entries of the Table 8.14 (rounded to two decimal places).

A - 1.00 B - 0.79 C - 0.48 D - 1.00 E - 0.98 F - 0.91

2a. Recall that this study assumed that a BAC of 0.04% or above means that a person is legally drunk. There were 296 participants in the study, and part of the table is already filled out for the participants who were legally drunk. Use the rule that any score in any of the three categories that is a "2" or higher meansthe roadside test tagged the participant as drunk. What are the values of the missing entries in Table 8.11?

A - 2 B - 27 C - 29 D - 4 E - 292

3c. Patients with suspected hypothyroidism were screened by Goldstein and Mushlin (J. Gen. Intern. Med. 1987;2:20-24) using thyroxine levels, often abbreviated as T4. Thyroxine is a hormone secreted into the bloodstream by the thyroid. The authors looked at three cutoff values for thyroxine level: 5 or less; 7 or less; 9 or less. With these three cutoffs they found the following: A plot of sensitivities (along a y-axis) versus FPRs (along an x-axis) for different rules is called a receiver operating characteristic curve (ROC). An ROC is a convenient way of deciding what cutoff rule is best for a particular screening test. Which of the following plots shown below is the correct ROC plot for the hypothyroid study?

ROC plot - graph B

1f. What might be the consequences of the FOB saying "negative" when the patient really did have bowel cancer?

a patient with a potentially fatal disease might be deprived of the quickest postscreening intervention possible.

1c. What percentage of the time did the FOB make the wrong decision?

about 9%

1d. What might be the consequences of the FOB screening test saying "positive" when the patient really didn't have bowel cancer?

this would potentially create unnecessary anxiety for the patient