## (solution) Week 2 - Quiz 2 Time Remaining: Question 1. 1. In a screening

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Week 2 - Quiz 2 Time Remaining: Question 1. 1. In a screening test, the probability of a person with the disease having a positive test is:

(Points : 1)

Sensitivity

Specificity

Positive Predictive Value

Negative Predictive Value Question 2. 2. If 2-stage testing is performed such that only subjects who are positive for both tests are

considered positive, what is the net impact on sensitivity and specificity? (Points : 1)

Sensitivity and specificity will both increase

Sensitivity and specificity will both decrease

Sensitivity will increase; specificity will decrease

Sensitivity will decrease; specificity will increase Question 3. 3. In a community with a population of 10,000 people, the prevalence of a certain disease

is 5%. A screening test for this disease with a sensitivity of 95% and specificity of 80% is implemented

on the entire population. How many TRUE POSITIVE results will there be? (Points : 1)

475

500

1900

7600 Question 4. 4. In the scenario from #3, what is the positive predictive value? (Points : 1) Question 5. 5. Two radiologists review the same set of x-rays for signs of lung cancer. If radiologist A

codes 25 as positive and 75 as negative, and radiologist B codes 32 as positive and 68 as negative, how

many x-rays would we expect them to agree on, just by chance? (Points : 1)

8

24

57

59 Question 6. 6. The case fatality rate is calculated as: (Points : 1)

The number of people who die of a disease divided by the number of people who have the

disease

The number of people who die of a disease divided by the number of people at risk of

developing the disease

The number of people who die of a disease divided by the total number of deaths

The total number of deaths in a community divided by the total population size Question 7. 7. The 5-year survival rate is usually used for: (Points : 1)

Short term, acute conditions

Evaluation of cancer treatment

Traumatic injuries

Patients diagnosed within the last five years Question 8. 8. In a study examining the survival of cancer patients, 100 patients were enrolled at baseline. After one year, 20 patients were known to have died. Assuming no patients were lost to

follow-up, what was the probability of surviving one year? (OK to show numerator/denominator)

(Points : 1) Question 9. 9. What would be the one-year survival rate in the previous question if ten patients had

been lost to follow-up during the first year? Use the life table method. (Points : 1) Question 10. 10. Suppose we are doing a study of survival using the Kaplan-Meier method. The study

enrolled 10 patients at baseline, and the first death occurred after five weeks. If two patients were lost

to follow up before this death was recorded, how do we calculate the proportion who died at that point

in time? (Points : 1)

1/10

2/10

1/8

1/7 Question 11. 11. In a randomized clinical trial, patients are assigned to their treatment group: (Points :

1)

On a first-come, first served basis

Alternately (patient 1 and every odd patient goes to group A, every even numbered patient is in

group B)

According to the severity of their illness

Randomly Question 12. 12. In a randomized trial, who should be blinded to which treatment group the patient is

assigned? (Points : 1)

The patient The person providing the treatment

The person interviewing the patient

All of these Question 13. 13. In a crossover design, controls are: (Points : 1)

The patients themselves

Randomly assigned

Previous patients (historical controls)

Friends of the patients Question 14. 14. ?Intention to treat? is when patients are analyzed: (Points : 1)

According to their originally assigned treatment group

According to their actual behavior, regardless of assignment

Before they actually begin treatment

As their own controls Question 15. 15. The probability of wrongly concluding that two treatments are significantly different is

known as: (Points : 1)

Type I error

Type II error

Power

Significance Question 16. 16. Suppose we are calculating the required sample size for a randomized trial. Which of

the following would increase the required sample size? (Points : 1) Increasing the expected effect size (the difference in response rates)

Decreasing the expected effect size

Decreasing the power

Increasing the size of our grant Question 17. 17. The comparability of our study sample to the population that we ultimately want to

treat is known as: (Points : 1)

Internal validity

External validity

Reliability

Efficacy Question 18. 18. A phase ____ clinical trial is a small study that seeks to determine whether a new

treatment may have toxic effects (Points : 1)

I

II

III

IV Question 19. 19. All monitoring of a drug?s effects stop after it has entered the consumer market

(Points : 1)

True

False Question 20. 20. All clinical trials of medical interventions are required to be registered in a public trials

registry before any participants are enrolled in the study (Points : 1) True

False Time Remaining:

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Sep 13, 2020

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